I suppose you're using an layout without auto-picking panel colors - in this case heart is red when clicked and it works fine.
However, when in auto-picking panel colors option, I have it like this:
The differecne between clicked and unclicked heart is merely visible (and much smaller than between clicked and unclicked stars).
Another issue worth mentionig are the borders of this panel - as on this screenshot:
It occurs while in auto-picking panel colors mode as well. Notice that when MB is in fullscreen, the colour belt goes through the whole width of the window. When not in fullscreen, those grayish stripes that I marked on the screenshot appear.
Btw: would it be difficult to create a kind of a generator of your skin? DarkMOD skin used to have it, however the generator page is currently down (EDIT: IT'S BEEN UPDATED AND WORKS AGAIN). Here's the thread:https://getmusicbee.com/forum/index.php?topic=17373.0