The Luma command returns the luma of a Color object, which is a float between $0.$ and $1.0$ representing the lightness of a color with $1.0$ being white and $0.$ being black.

The calculation is performed using the formula $\mathrm{Y\; \'}=0.3R+0.59G+0.11B$ where (R,G,B) is the RGB triple for the color.

$c≔\mathrm{ColorTools}:-\mathrm{Color}\left(''green''\right)$

$c≔⟨RGB\; :\; 0\; 1\; 0⟩$

$\mathrm{Luma}\left(c\right)$

$0.590000000$

The ColorTools[Color][Luma] command was introduced in Maple 2017.

For more information on Maple 2017 changes, see Updates in Maple 2017.