These colors must match the number and the gender of the noun which they modify:

bianco = white

nero = black

rosso = red

giallo = yellow

grigio = gray

camicia bianca = white shirt

pantaloni bianchi = white pants

vestito bianco = white dress

scarpe bianche = white shoes

These colors must match the number only of the noun which they modify:

verde = green

marrone = brown

celeste = sky blue

arancione = orange

abito marrone = brown suit

cravatta marrone = brown tie

pantaloni marroni = brown pants

scarpe marroni = brown shoes

These colors will never change:

blu' = blue

rosa = pink

viola = purple

vestito blu' = blue dress

scarpe blu' = blue shoes

vestito viola = purple dress

scarpe rosa = pink shoes