Melanism: This is an increased amount of black or nearly black pigmentation (as of skin, feathers, or hair) caused by an elevated concentration of melanin. It's like having an overactive color printer that only prints in black!
Camouflage:This is when organisms blend with their surroundings by means of coloration. Imagine if your clothes automatically changed to match your surroundings - that's what camouflage does for animals!
Sexual Selection: This is natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. Like how you might be attracted to someone who dresses well, some animals are attracted to mates with specific colors.