I emailed the person who chose the colour scheme for the Soundloom interface, and he said that has no problem using the Leeds colour on his Mac, or in changing the colour scheme through System State>System Settings 1 > Color Style. Now I tried to change the colour this way many times without success. So I tried something different. I changed it, closed and opened (with no change), then Force Quit, and opened, closed and opened again, and it changed. What a relief! I don't know what I did that made the difference, either multiple close/opens after changing the Color Style, or the Force Quit.