If you do have several roles, you will get the color of the highest role. The roles & colors are hierarchical. So, lower roles will inherit the attributes (such as the color) from higher roles. You can change the hierarchy of the roles with a simple drag & drop in the roles list ("Server settings" and then head over to "Roles"). There, the first role in the list is the highest role and the last role in the list represents the lowest role. To change the hierarchy, simply drag & drop the role to a different position in that list.