Hi @alvaro624la , I will reply in eng as my spanish is not good enough to write a reply in it 
Anyway your logic is correct, but you have two possible errors:
1 - “ seems you are using a weird formatted double quotes. Make sure to use the standard ".
2 - cambioColores(azul) You have to remember that you need to pass a string to the function. So the word azul should be wrapped in quotes: cambioColores("azul")
Hope this helps