Break down of cloroplasts send the plants into flower faster. Yellow light breaks down cloroplasts. I have read experiments about flowering with low pressure sodium lamps that produce a pure yellow light from the inner bulb and a 15% red spectrum according to a contact at Phillips Neitherlands division where the specialty bulbs are manufactured, due to a IR coating which insulates the bulb tips, which as you know is where most of the heat is lost. Older models of the low pressure sodium bulbs used tin plates to insulate the tip which produces a blue spectrum. Regardless the LPS bulbs force flowering quickly but the plants reach and strech as it is a unbalanced spectrum. Plants use only a small portion of red light which is seen in the morning light during autumn due to the tilt of the earth and angle the light from the sun is passed through the gases of the atmosphere. The degree kelvin of the sun around noon in most parts of the globe is around 5500 degrees K. Since the plants did not evolve under 2100 K seen in a HPS or 3200 K as mentioned above the most balanced spectrum is a 5150 K. As far as length of the budding cycle it may be a bit longer as MH is a fraction longer then HPS, but in terms of produces the most natural spectrum the bulb above seems to take the cake.

The 2100 K is almost a pure orange.
3,000,000/2100=1428
1428-750=678 Nanometers
orange is 669.6 nanometers

The 3200 K is the middle of the ultraviolet spectrum where green would be in the visable light spectrum so it looks blue
3000000/3200=937.5
937.5-750=187.5 then convert that into the visible spectrum
750-187.5=562.5 nanometers (could just do 937.5-375 but did not want to ad to the confusion)

5150 K which is about 5.3% red(723NM), 36.3% blue(508NM), and 58.3% yellow(616NM) if you average the nanometers (distance measurement of the wave lengths)
3000000/5150=582 being slightly more yellow light then blue. More visible light spectrum then infrared or ultra violet versions.

I hope that helps
One love
c