Colours
Divided according to their endings
a) -o (masculine)/-a (feminine):
amarelo/a - yellow
branco/a - white
castanho/a - brown
cinzento/a - grey
dourado/a - golden
encarnado/a ou vermelho/a - red
roxo/a - purple
b) one form for singular (fem/masc) + one form for plural (fem/masc):
azul → azuis - blue
caqui → caquis - khaki
verde → verdes - green
c) one single form for both gender and number:
co-de-laranja - orange
co-de-rosa - pink
violeta - violet