Questions & Answers about La scritta rossa sul muro è grande.
In Italian, most adjectives follow the noun they modify:
• La scritta = the inscription (noun)
• rossa = red (adjective)
The ending -a shows agreement in gender (feminine) and number (singular) with scritta.
Sul is a contraction of the preposition su (“on”) + the definite article il (“the”, masculine singular):
su + il → sul
So sul muro literally means “on the wall.”