Which colours may be placed around red to make it more prominent in a painting?

Correct answer: Cool colours

The governing concept is warm–cool contrast and visual emphasis. Red is generally a warm colour, so placing it beside cool colours such as blue, blue-green or violet can increase contrast and make the red focal area stand out. Lighter reds create a related monochromatic effect, while orange and yellow are also warm neighbours and usually provide less warm–cool contrast. Thus, cool colours are the most suitable general answer.