I am a very strong advocate in the single color spectrum. 3500k have every one of these colors people try to purchase separately all mixed into one light. This makes blending a non issue too. I feel any additional colors or spectrums should only really be used to suppliment a specific peak the original light may not have. For example most lights based on the 3500k spectrum have plenty of blue and red. Some lights may have less red or less blue than others. Which ever is lacking would be a good candidate for a supplement. Another reason to supplement would be if you were doing poorly vegging but produced very thick dense buds, maybe a higher temp would help. Or if you grew 6 foot tall bushes with all larfy buds maybe a lower temp would help.