Gender of colours

[fglorca]

All the adjectives of colour below end in ‘-a’, but only some of these also act as a noun.

- fucsia - fucsias
- lila - lilas
- magenta - magentas
- mostaza - mostazas
- naranja - naranjas
- púrpura - púrpuras
- rosa - rosas
- siena - sienas
- terracota - terracotas
- turquesa - turquesas
- violeta - violetas

Is it correct to say that none of these has a gender change i.e., they always end in ‘-a’ for the singular?
Is it also correct to say that the plural can be formed for all of these by simply adding ‘-s’?
In other words, can these adjectives appear in sentences like these ones:

- No me gustan los bolsos turquesas.
- Prefiero los abrigos violetas.

Some sources say you don’t add an ‘-s’ to form the plural, but others say you do.

Many thanks in advance.