Is there a maximum number of color range i can use in a space (residential/commercial) and how best can I mix colors in interior design?

It depends on the space that ur working on, it clear that

in residental space u have more opt for choosing , mixing colors but

in commercial space the main objective is to maximize exposue and if we use wide range of mixing colors it could be annoying.

There is no limit of color that will be used for finishing the house or interior space .. but at least some color gradations would be no more suitable example for4 color .. you should avoid manually mix multiple colors because it will result in non-standard colors.