Black coat will be much more interesting if you replace it with cream or blue. Sure, you have to look out for combining with other colors, but bright colors does not restrict as much as you think.
Blues, greens or purples hues can combine them with neutral tones, classic black and white and gray combination, and the darkest shades of any color. Violet can coat looks great with dark blue pants and a gray sweater. Green cape wear with gray pants, a simple shirt and high boots.
There are countless combinations and ideas on how to wear colorful gowns, just do well to consider that prevailing colors in your closet. Appropriately them renew with patterned gown.