Race, nationality, color and ethnicity are all different categories. Some people might have sensitivities to the use of color when describing a person while most do not. Generally, other than describing a person as white or black no other usage of color is acceptable in English. Some people might ask for example- Who did you talk to? The white guy or the black guy? While it is usually socially acceptable in most situations there can be cases where such a usage may come across as offensive. Using any other color ie. yellow, would be both awkward and possibly offensive. Using dark to describe someone would be offensive. Using light-skinned, dark-skinned, fair-skinned, tanned or pale as a general skin tone variation is usually not offensive. If the person you are describing does not fit into the categories of white or black and you don't have any other means of describing them as an individual you can use their racial/ethnic category in some cases. To do this you can say I think he/she was....(race/ethnicity) or add (-looking) to the racial category. Example- He was a(n) Hispanic/Asian/etc.-looking gentleman. or I think she was Hispanic/Asian/etc.

Sorry, I don't understand your first question.