color utils: fix compilation on Qt < 5.14
Continuing from merge request !8 (closed) :
- fixed Qt version check (great idea, I like it!); removed commented code
- fixed commit message
@pino this new merge request should fix all the issues with the previous merge request. Feel free to merge if you are comfortable with it.
Apparently I couldn't force-push the original branch, so I created a new merge request.