Learn Hardcore Finnish: Minusta tämä maalaus on todella värikäs. - In my opinion this painting is really colorful.

Literally, minusta is minä (I) in the elative case (the case with the ending -sta / -stä, often meaning out of / from). So the most literal idea is from me or from my point of view.

In Finnish, feelings, judgments, and opinions are often expressed with a structure like:

Minusta tämä maalaus on todella värikäs.
= From me / from my point of view, this painting is really colorful.
→ Natural English: I think this painting is really colorful. or In my opinion, this painting is really colorful.

So minusta does not literally mean I think, but the structure minusta + sentence functions as a common way to express a personal opinion.

What is the difference between minusta and minun mielestäni?

Both can translate as in my opinion or I think, but there are nuances:

Minusta tämä maalaus on todella värikäs.
Very common, neutral, slightly shorter and more colloquial-sounding in everyday speech.
Minun mielestäni tämä maalaus on todella värikäs.
Literally: in my opinion (from my mind / from my view).
Feels a bit more explicit and sometimes a bit more formal or careful.

Meaning-wise, they are very close. You can usually substitute one for the other:

Minusta tämä maalaus on todella värikäs.
Minun mielestäni tämä maalaus on todella värikäs.

Both are correct.

Why is it minusta (with -sta) instead of just minä or minun? What is that -sta ending?

The -sta / -stä ending is the elative case, usually meaning out of, from inside, or more abstractly from the point of view of.

Some patterns:

minä → minusta (from me / in my view)
sinä → sinusta (from you / in your view)
me → meistä (from us / in our view)

Finnish uses this case to express who an opinion or feeling comes from:

Minusta tämä on hyvä.
From me → In my opinion, this is good.

So minusta is the grammatically normal way to say in my opinion in this structure; using minä or minun alone would be incorrect here.

Could I say Tämä maalaus on todella värikäs minusta instead? Is that acceptable?

Yes, it is grammatically correct:

Tämä maalaus on todella värikäs minusta.

However, the most typical and natural order for this opinion-structure is to put minusta first:

Minusta tämä maalaus on todella värikäs.

Placing minusta at the start foregrounds that what follows is your personal perspective. Putting minusta at the end is possible, but sounds a bit more like an afterthought or emphasis:

Tämä maalaus on todella värikäs, minusta.
(Spoken with a pause, like: This painting is really colorful, to me.)

For learners, the safest and most natural choice is to use Minusta + sentence.

Why is it tämä maalaus and not tämän maalaus?

Tämä is the nominative singular form of the demonstrative pronoun, used for the subject:

tämä maalaus = this painting (subject)

If you used tämän, that would be a genitive form (like of this):

tämän maalauksen kehys
= the frame of this painting

In your sentence, tämä maalaus is simply the subject of the verb on, so both words (tämä and maalaus) appear in nominative:

Minusta tämä maalaus on todella värikäs.
tämä maalaus = this painting (subject)

Why is maalaus in this form? Could it be maalausta or maalauksen instead?

Here maalaus is in the nominative singular form, because it is the subject of the sentence:

Tämä maalaus = this painting (subject)
on = is (linking verb)
todella värikäs = really colorful (predicate adjective)

You would use other forms in different roles:

maalausta (partitive):
- Katson maalausta. → I am looking at the painting.
maalauksen (genitive):
- Maalauksen kehys on kaunis. → The frame of the painting is beautiful.

In Minusta tämä maalaus on todella värikäs, we are describing the subject, so maalaus stays in nominative.

What is the role of on in this sentence? Why is it not connected to minä somehow, like minä olen?

On is the 3rd person singular of the verb olla (to be). Here it is simply the linking verb connecting the subject (tämä maalaus) to the description (todella värikäs):

Tämä maalaus on todella värikäs.
This painting is really colorful.

Minusta is not a subject; it is an adverbial of opinion (from my point of view). The grammatical subject is tämä maalaus, so the verb must agree with that:

Subject: tämä maalaus (3rd person singular)
Verb: on (3rd person singular of olla)

Finnish does not use a structure like I am thinking that here. Instead, it says:

Minusta (from me / in my opinion) + tämä maalaus on todella värikäs.

What is the difference between todella, tosi, erittäin, and hyvin when meaning really / very? Could I replace todella here?

All of these can intensify an adjective like värikäs, but they differ in tone and frequency.

In your sentence, you could say:

Tämä maalaus on todella värikäs.
Neutral, quite common. todella originally means truly / really.

Other options:

Tämä maalaus on tosi värikäs.
Very common in colloquial speech; tosi sounds a bit more informal and conversational.
Tämä maalaus on erittäin värikäs.
More formal, can sound a bit stronger or a bit more written / careful.
Tämä maalaus on hyvin värikäs.
Also possible; hyvin literally means well, but as an adverb it can mean very. In some contexts, it can sound a bit old‑fashioned or literary when used like this.

All four are grammatically fine; the main difference is style and register, not basic meaning.

What does värikäs exactly mean, and why is it in this form (not värikasta)?

Värikäs is an adjective meaning colorful (literally color-y, full of colors).

In a sentence like:

Tämä maalaus on todella värikäs.

värikäs is used as a predicate adjective describing the subject (tämä maalaus). Finnish normally uses the nominative form of the adjective here:

Maalaus on värikäs.
Talo on suuri.
Elokuva oli hauska.

You would use other forms depending on case and number:

värikäs maalaus (a colorful painting)
värikkäitä maalauksia (colorful paintings, partitive plural)
värikkään maalauksen (of the colorful painting, genitive)

Here, since it is just describing the nominative subject, it stays in the nominative värikäs.

Can I drop tämä and just say Minusta maalaus on todella värikäs?

Yes, that is possible and grammatical:

Minusta maalaus on todella värikäs.

The difference is in how specific you are:

Minusta tämä maalaus on todella värikäs.
Refers to a clearly indicated specific painting (this painting).
Minusta maalaus on todella värikäs.
Could mean:
- a painting previously mentioned in context, or
- painting as an art form in general, depending on context.

If you want to clearly point to one particular painting (for example one you are looking at), tämä maalaus is more explicit.

Can I just say Maalaus on todella värikäs without minusta? What changes in meaning?

Yes, you can:

Maalaus on todella värikäs.
= The painting is really colorful.

Without minusta, the statement sounds more objective, like a description of a fact.

With minusta:

Minusta tämä maalaus on todella värikäs.

you are explicitly marking it as your personal opinion or impression. In real-life conversation, context and tone often make it clear that something is an opinion, so native speakers frequently omit minusta when it is obvious. But including minusta makes the subjectivity explicit.

Is Minusta tämä maalaus on todella värikäs more like I think that this painting is really colorful or To me, this painting is really colorful?

It can correspond to both, depending on context and tone:

I think (that) this painting is really colorful.
→ very natural translation; focuses on your judgment.
To me, this painting is really colorful.
→ a bit closer to the literal idea (from me / from my point of view); can suggest that others might see it differently.

In Finnish, minusta always carries that nuance of personal viewpoint, so when translating, you can usually choose whichever English version fits the context better.