I did a little experiment recently, using a 4' , 2-tube, flourescent fixture.
In one socket I put a 'plant and aquarium' light, wondering if those things are worth the $8 each they cost. Oh, and BTW they put out a pinkinsh light.
In the other I put a cool white tube.
I centered the seedlings in a row directly below the fixture.
Within 24 hours, all the seedlings were bending and stretching towards the cool white side.
I guess they just like it better!!!!