Learn Finnish: Muistaakseni setä värittää näitä sukutarinoita paljon. - As far as I remember, uncle colors these family stories a lot.

It is built from the first infinitive of the verb muistaa (to remember), plus the translative case marker -kse-, and the first-person singular possessive suffix -ni. It functions as a fixed sentence adverb meaning 'as far as I remember' or 'to my recollection.'

If I wanted to talk about someone else's memory, how would that first word change?

You simply change the possessive suffix to match the person. For example, 'as far as he remembers' or 'as far as she remembers' would be muistaakseen, using the third-person suffix. 'As far as you remember' would be muistaaksesi.

Why is näitä sukutarinoita in the partitive plural instead of the accusative?

The verb värittää (to color or embellish) describes an ongoing, open-ended activity here, rather than a completed action that permanently finishes the stories. Because this embellishing is continuous and applies to an indefinite amount of the stories, the object requires the partitive case.

Is värittää naturally used for 'embellishing' in everyday Finnish?

Yes, while värittää literally means to color a picture, it is extremely common in Finnish to use it metaphorically for exaggerating or adding dramatic, untrue details to an account, much like saying someone 'colors the truth' in English.