Answer:
a. tint
Step-by-step explanation:
Tint refers to a a shade or variety of color which is created by being added white. As a result, the color obtained has a paler variety than the original one.
The rest of the options are incorrect because depth indicates that the color is darker and stronger; shade involves the type or degree of a color; while tone refers to the degree or quality of brightness, deepness or hue of a tint or shade of a color.