This package currently calculates the average color, not the dominant color.

Average colors for most images are muddy brown.

The dominant color for an image is found by extracting the most-used color from a reduced-palette (or "quantized") version of an image.

We'd expect green to be the dominant color for this image:

but

$ convert test.jpg -scale '1x1!' -format '%[pixel:u]' info:-
srgb(108,107,83)

Quantizing the palette to 32, and looking for the most-seen color, though, produces

$ convert test.jpg -scale '32x32' +dither -colors 32 -define histogram:unique-colors=true -format "%c" histogram:info: | sort -nr | head -1 | awk '{ print $4 }'
srgb(135,152,101)

Much better!

Here's the output without the sorting and awking:

$ convert test.jpg -scale '32x32' +dither -colors 32 -define histogram:unique-colors=true -format "%c" histogram:info:
        51: ( 23, 24, 25) #171819 srgb(23,24,25)
        12: ( 29, 30, 34) #1D1E22 srgb(29,30,34)
        24: ( 30, 34, 38) #1E2226 srgb(30,34,38)
        50: ( 44, 44, 44) #2C2C2C srgb(44,44,44)
        18: ( 74, 56, 53) #4A3835 srgb(74,56,53)
        21: ( 81, 76, 55) #514C37 srgb(81,76,55)
        35: ( 86, 76, 72) #564C48 srgb(86,76,72)
         1: ( 92, 40, 52) #5C2834 srgb(92,40,52)
         3: ( 95, 62, 65) #5F3E41 srgb(95,62,65)
        16: ( 97,104, 81) #616851 srgb(97,104,81)
        12: (103, 83, 60) #67533C srgb(103,83,60)
        34: (106, 85, 77) #6A554D srgb(106,85,77)
        26: (109,131, 83) #6D8353 srgb(109,131,83)
        43: (111,107, 81) #6F6B51 srgb(111,107,81)
        37: (118,138, 89) #768A59 srgb(118,138,89)
        25: (121,110,104) #796E68 srgb(121,110,104)
        20: (123,143, 97) #7B8F61 srgb(123,143,97)
        50: (124,146, 92) #7C925C srgb(124,146,92)
        26: (130,147, 94) #82935E srgb(130,147,94)
        21: (133,109, 88) #856D58 srgb(133,109,88)
         1: (133, 55, 60) #85373C srgb(133,55,60)
       102: (135,152,101) #879865 srgb(135,152,101)
        47: (143,120,107) #8F786B srgb(143,120,107)
        17: (149,161,118) #95A176 srgb(149,161,118)
        18: (149,140,113) #958C71 srgb(149,140,113)
         6: (149,100, 89) #956459 srgb(149,100,89)
        29: (162,137,119) #A28977 srgb(162,137,119)
        20: (169,149,142) #A9958E srgb(169,149,142)
         3: (202,193,195) #CAC1C3 srgb(202,193,195)

There's almost no additional expense to doing it "correctly", also. The first command ran in 0.030s, the the second (correct) command ran in 0.036s.

shime / dominant-color

This package currently calculates the average color, not the dominant color. #2