Basic colors
  black   red   blue   green   magenta   cyan   yellow   white 
  black   red   blue   green   magenta   cyan   yellow   white 

Effects
  red   bold red   underline on blue   on green   on bright green   inverse 

color0 - color15
  0 1 2 . . .
                  
                  
          . . . 15

Color cube rgb000 - rgb555 (also color16 - color231)
  0            1            2            3            4            5
  0 1 2 3 4 5  0 1 2 3 4 5  0 1 2 3 4 5  0 1 2 3 4 5  0 1 2 3 4 5  0 1 2 3 4 5
 0                                                                              
 1                                                                              
 2                                                                              
 3                                                                              
 4                                                                              
 5                                                                              

Gray ramp gray0 - gray23 (also color232 - color255)
  0 1 2 . . .                             . . . 23
                                                  

Try running 'task color white on red'.