Anything under 5150 is yellow light. Anything over is considered blue. 5150 is the K that the sun is. Yellow breaks down cloroplasts into sugar then starch while blue builds the cloroplasts. Plants need 5.3%red light 36.3%blue and 58.3%yellow. A pure yellow spectrum bulb (besides the 15%red do to the ir coating which insulates the tip) is the low pressure sodium and it is the most efficent light ever made at 200 lumens per watt. People have tryed to flower under them and although it forces plants into flowering faster by breaking down more cloroplasts the plants grow to stringy as they are starved for food. A pure blue spectrum is the xenon bulb.

When I veg I give 24 hour light which is most important with mothers if you want them to last genetically.