The foreground is gray (black character), and what color is suitable for the background (the character is a full-screen big picture, who can tell me how to do it?

Blood red is good ~ as red control ~ ~OWO

But if the foreground is gray-black, it depends on what style you want to make.

If it is dark, use a darker color, such as navy blue. . Deep red ~

If you want to stimulate, use especially bright colors, such as fresh grass green and yellow ~

Anyway, don't use too moderate colors, dark or light, depending on the specific situation.