it is a more close representation of the autumn or late summer sun which is stronger in the red spectrum than the spring and early summer sun. im no scientist, but it has something to do with where the autumn sun is in the horizon.
The blue in the light you are referring to is not an actual blue light bulb but the spectum of light given off by the daylight spectrum bulb. This actual blue light that is used by plants is not visible to the human eye.