glcolor4f()

Hi All¡¡¡¡¡¡

i´m using glcolor4f(red,green,blue,0.2) in order to see translucency objects. It works correctly, but the generation of the image is very slow. With complet colors the same graphics was showed inmediatly, but using this function and the alpha parameter go slowly.

What can i do?

thanks a lot.

PERE