Colour words are adjectives: they come after the noun and agree with it, adding -e for a feminine noun and -s for a plural (un sac vert, une robe verte, des chaussures vertes). Colours named after a thing, such as orange and marron, never change. Blanc has the irregular feminine blanche.
Examples
- Une voiture noire.
- A black car.
- J'ai les yeux verts.
- I have green eyes.
- Des chaussures marron.
- Brown shoes.
The mistake to avoid
Colour words go AFTER the noun: une voiture rouge, never "une rouge voiture".
Where this fits in
Colours, clothes & likes, French A1: Name colours and clothes, buy something in the right size, and say what you like and don't like.