Which colour scheme has light and dark versions of only one main colour?

Correct answer: Monochromatic scheme

The governing concept is colour harmony through variation within one hue. A monochromatic scheme uses one main colour and develops a range from it by using its tints, shades, and sometimes tones. For example, a blue monochromatic design may contain pale blue, medium blue, and navy blue while remaining visually connected. Therefore, option B is correct. A complementary scheme combines colours opposite each other on the colour wheel, such as blue and orange. A triadic scheme uses three colours spaced at roughly equal intervals on the wheel, so it is not limited to one hue. “Colourless scheme” is not the standard name for this relationship and would not describe light and dark versions of a colour. The prefix mono means one, which is a useful memory clue.