masculine & feminine

Hola Iris

Some colours have a different form for masculine and feminine (-o, -a) and some other colours only have one form for both (e.g naranja, rosa...). On that list you can see some colours with the two forms. e.g. amarillo/ amarilla, and other like naranja with just one form. 

We also have a lesson about colour and their endings where you will find a table with them illustrating this. Have a look here.

I hope it helps.

Saludos

Inma