To make most French nouns plural, add -s: un livre, des livres. The -s is silent, so you hear the plural in the article (le/les, un/des), not in the noun. Nouns that already end in -s, -x or -z do not change (un pays, des pays). Nouns ending in -eau or -al change to -eaux and -aux: un manteau, des manteaux; un journal, des journaux.

Colours are adjectives, so they agree with the noun: add -e for feminine and -s for plural. Some change their spelling: blanc becomes blanche, and vert, noir, bleu and gris simply add -e (verte, noire, bleue, grise). Colours ending in -e, like rouge and jaune, stay the same in the feminine and just add -s in the plural.

Colours go after the noun: une robe rouge, not une rouge robe. English speakers often forget the agreement: say les chaussures noires, not les chaussures noir.