Colours as adjectives

[Myr1991]

My grammar book and dictionary are confusing me. My grammar book says:

Some adjectives and other parts of speech when used adjectivally never change in the feminine or plural.
The commonest of these are:

- nouns denoting colour
- compound adjectives
- nous used as adjectives

"Nouns denoting colour" is what's confusing me. The example that my grammar book gives is "los vestidos naranja". Vestidos is masculine plural but naranja doesn't change.
Tha's clear, I thought. Easy to remember.

But then I looked in my dictionary. There's some grammar in the back of my dictionary and at the part about adjectives the examples are:
- un libro amarillo
- libros amarillos
- una casa amarilla
- casas amarillas

So colours do change to feminine and plural according to my dictionary.

So I'm confused. Which one is right, my grammar book or my dictionary? Can someone explain?

 

[blasita]

Cuando funcionan como adjetivos, hay que distinguir entre los nombres que designan únicamente colores, los cuales concuerdan siempre con el sustantivo al que modifican (faldas rojas, pantalones verdes, ojos azules,etc.), y los nombres que designan primariamente una flor, un fruto, una sustancia o un objeto que tienen ese color característico, los cuales pueden usarse en aposición y permanecer invariables en plural (ojos malva, faldas naranja, camisas añil, etc.) o concordar con el sustantivo, con funcionamiento plenamente adjetivo (ojos malvas, faldas naranjas, camisas añiles, etc.).

Colours -when they work as adjectives- agree with the nouns they modify. Your grammar book may refer to what I've highlighted in blue; in this case, they can follow the noun and be invariable. So, taking your example: here you can say 'los vestidos naranja' and 'los vestidos naranjas'.

More information: DPD.

Saludos.