I'm sorry for late answer.
I explain how to make color in a small illumination.
step1, open 8bit gray scale image.
step2, change color mode to RGB color.
step3, To obtain the color for which you hope,
correct level to differ respectively in each RGB channel.
It is decided whether the color is beautiful by your sense.
The samples for the adjustment is displayed as follows.
Basic cross(modified for more accurate glow),
Type-3