A chosen set of colors is known as the

I think the answer is color theory

Explanation:

In color theory, a color scheme is the choice of colors used in various artistic and design contexts. ... The addition of light blue creates an "Accented Analogous" color scheme.

domes and arches have a specific esthetic look and feel. that is very important in architecture. churses and cathedrals are usually also large spaces and arches and domes is a good way to distribute the weight so that the rooms can be larger to hold more people. they are also beautiful and can be in many different forms so the architects can create art with them inspiring feelings in people.