The most colorful mums require a minimum of three hours a day of intense direct lighting. According to SFGate, mums will need full sun conditions to perform best, with the intensity and duration of light directly affecting bloom quality.
Mums that have more shade will not be as robust as their counterparts kept in full sun. Shade-grown mums aren't able to support as many flowers during the summer, while bushier, full-sun mums are stout and can support several flowers. Keep mums well-watered when they are in full sunlight, and water them less if they have more shade.