Changing an individual applet's colours or size in panels in Mate

[mttr]

The problem is some applets i.e. separators are next to impossible to see to move or remove from the panel bar. I have tried changing the background colour but the only way has been with some limiting success was to change the Panel properties background to none. The separator is barely if not invisible. Changing the size of the panel does not enlarge the separator applet. If the that applet could be made a temp different colour that would help a lot.