What type of color is observed when a compound absorbs red coloured light?

When a compound absorbs a specific color of light from the visible spectrum, the color it exhibits (observed color) is the complementary color of the absorbed light.

According to the complementary color wheel, the complementary color of red is blue-green (or cyan). For example, hydrated copper(II) complexes absorb red light and appear blue.

Since blue-green is not explicitly given in the options, blue is the most appropriate and closest choice.

Answer: Blue