In spanish,when you form plural,you add es or s?please give me some example!?

ok it depends see like for colors you have to plural them but if any word your are trying to make plural if it ends in a consistent not a e i o u its a s but if its a e i o u its es here are examples
For exaple: paper (papel) and in plural is papeles.
It always depends on the word , but usually just s but if it is a word that ends in z you have to add (ces) ;and in ocassions the es

Examples:

1- Libro (Book) -Libros , just the es was added

2-Pez(Fish)- Peces, i added the (ces)

3-Mujer(woman), Mujeres, i added th es

The es is addd only when the word doesn