How Many Red, Green, and Blue LEDs to make White

And How Much Current They Need

Statements and Assumptions of Specific LED Types

Green LEDs mentioned below are Nichia NSPG series of brightness rank T and color rank G (their usual shade of green with dominant wavelength of 525 nm), specifically NSPG-500S-GT in the case of 5 mm 15 degree lamps. Luminous output is assumed to be 2.6 lumens at 20 mA. CIE chromaticity is x=.17, y=.7, z=.13. Typical voltage drop 3.6 volts at 20 mA.

"Regular" blue LEDs mentioned below are Nichia NSPB series of brightness rank T and color rank W (their usual shade of blue with dominant wavelength of average units being being 471 nm), specifically NSPB-500S-WT in the case of 5 mm 15 degree lamps. Luminous output is assumed to be .55 lumen at 20 mA. CIE chromaticity is x=.13, y=.075, z=.795. Typical voltage drop 3.5 volts at 20 mA.

Alternative blue LEDs mentioned below are Nichia NSPB series of brightness rank S and color rank V (deeper than their usual shade of blue, with dominant wavelength of average units being 462 nm), specifically NSPB-500S-VS in the case of 5 mm 15 degree lamps. Luminous output is assumed to be .45 lumen at 20 mA. CIE chromaticity is x=.145, y=.055, z=.800. Typical voltage drop 3.6 volts at 20 mA.
It is to be noted that the "blue impact" of Nichia's VS rank is greater than that of their more popular, more available WT rank despite lower photometric output since the V rank's spectral output is a better match to the spectral response of the blue receptors of the human eye.

Percentage of Total LED Count When All LEDs Get 20 mA

Color    % of LEDs R, G, B     Overall        % of LEDs R, G, B    Overall
Temp.      with "regular"      Efficiency    with "alternative"    Efficiency
Kelvin    Nichia WT blue      lumens/watt     Nichia VS blue      lumens/watt

2700    63.5%R, 31.6%G,  4.9%B    26.9      63.5%R, 32.2%G,  4.3%B    27.0

  12/6/1 ratio is very close to 2750K     12/6/1 ratio is close to 2850K

3000    60.4%R, 32.8%G,  6.8%B    26.7      60.4%R, 33.6%G,  6.0%B    26.8
3500    56.2%R, 33.9%G,  9.9%B    26.3      56.1%R, 35.1%G,  8.8%B    26.4
4100    52.2%R, 34.4%G, 13.4%B    25.7      52.0%R, 36.0%G, 12.0%B    25.85
5000    47.8%R, 34.4%G, 17.8%B    24.8      47.4%R, 36.5%G, 16.1%B    25.05
5500    45.9%R, 34.1%G, 20.0%B    24.4      45.5%R, 36.5%G, 18.0%B    24.65
6500    43.1%R, 33.5%G, 23.4%B    23.65     42.4%R, 36.3%G, 21.3%B    23.95
9300    38.5%R, 31.7%G, 29.8%B    22.25     37.5%R, 35.2%G, 27.3%B    22.6

      1/1/1 ratio is close to 13000K      1/1/1 ratio is close to 16000K

The main reason is that the red LEDs have a 2 volt voltage drop while the green and blue ones have a 3.5-3.6 volt voltage drop and will consume 75-80 percent more power than the red ones will. Also, the blue ones put out almost 50 percent more radiometric output than the green ones do.
The "regular" Nichia blue LEDs of color rank W are slightly cyanish and will reduce green requirement, as opposed to Nichia's less common V rank which is closer to pure blue. But since Nichia's G-rank greens are slightly whitish, forcing increased use of these green LEDs by use of a purer blue can reduce requirements of blue and/or red. V-rank reduces blue requirement (compared to W-rank) also by being better at stimulating the blue receptors of human vision than the W-rank blue is.

Wondering why overall luminous efficacy here is maximized at lower color temperatures in the upper 2,000's Kelvin, while a blackbody has highest luminous efficacy in the 6,000's Kelvin?

The answer here is that blackbodies radiate heavily in the infrared while LEDs do not. A 3000K blackbody has over 90 percent of its output in the infrared. With an LED combination, highest overall luminous efficacy is achieved by using the most with more luminous efficacy (green and secondarily red) and less of what has the lowest luminous efficacy (blue).

Percentage of Total LED Count for Various Shades of White When Red LEDs Get 30 mA and Green and Blue LEDs Get 20 mA

Color    % of LEDs R, G, B     Overall        % of LEDs R, G, B    Overall
Temp.      with "regular"      Efficiency    with "alternative"    Efficiency
Kelvin    Nichia WT blue      lumens/watt     Nichia VS blue      lumens/watt

2700    53.7%R, 40.1%G,  6.2%B    26.9      53.7%R, 40.8%G,  5.5%B    27.0
3000    50.4%R, 41.1%G,  8.5%B    26.7      50.4%R, 42.1%G,  7.5%B    26.8

      6/5/1 ratio is close to 3000K      6/5/1 ratio is close to 3100K

3500    46.1%R, 41.8%G, 12.1%B    26.3      46.0%R, 43.2%G, 10.8%B    26.4
4100    42.1%R, 41.7%G, 16.2%B    25.7      41.9%R, 43.6%G, 14.5%B    25.85
5000    37.9%R, 40.9%G, 21.2%B    24.8      37.5%R, 43.4%G, 19.1%B    25.05
5500    36.1%R, 40.3%G, 23.6%B    24.4      35.7%R, 43.0%G, 21.3%B    24.65
6500    33.6%R, 39.0%G, 27.4%B    23.65     32.9%R, 42.3%G, 24.8%B    23.95
9300    29.5%R, 36.3%G, 34.2%B    22.25     28.6%R, 40.3%G, 31.1%B    22.6

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