I've tried clear/ black/ white and blue plastic on my garden and find that black isn't very useful since very little of the heat is transferred from the plastic to the ground, clear works much better.The blue worked great on my cucumbers but my peppers developed long, weak stems (This is only a 1 yr / 12 plant sample). After spending a little time this winter learning about how plants utilize different wavelengths of light during their life cycle I'm going to try something a little different. This year I'm putting down a layer of green plastic over a layer of red plastic, I'm hoping that the green will stimulate vegetative growth and then when the plants begin to fruit I'll remove the green and the red should stimulate fruiting, I hope.... The UMass extension has gathered some facts about colored mulches that you can read http://extension.umass.edu/landscape/...