Which mixture is useful for making a light peach-like colour?

Correct answer: Orange and white

The governing concept is tinting: adding white to a hue reduces its intensity and increases its lightness. Orange mixed with sufficient white can produce a light peach-like colour, with the exact appearance depending on the proportion and the pigments used. Blue with black becomes dark, green with violet is likely dull, and red with green tends toward a neutral or muddy mixture. Option A is correct.