private boolean isCorrectFunction(Variable variable, VTMarkupItem markupItem) {
		Function function = variable.getFunction();
		Address variableFunctionAddress = function.getEntryPoint();
		Program program = function.getProgram();
		VTAssociation association = markupItem.getAssociation();
		VTSession session = association.getSession();
		Program sourceProgram = session.getSourceProgram();
		Program destinationProgram = session.getDestinationProgram();
		if (program == sourceProgram) {
			Address markupFunctionAddress = association.getSourceAddress();
			if (!variableFunctionAddress.equals(markupFunctionAddress)) {
				return false;
			}
		}
		else if (program == destinationProgram) {
			Address markupFunctionAddress = association.getDestinationAddress();
			if (!variableFunctionAddress.equals(markupFunctionAddress)) {
				return false;
			}
		}
		else {
			return false;
		}
		return true;
	}
Creates a darker shade of the color passed-in, based on the given amount.

algorithm: 1) grab individual rgb elements
           2) multiply each by a factor.
           
           ie: int newRed = (int)(oldRed * 0.85);

@param color the color to shade
@param amount number between 0..1 (the smaller the number, the darker the shade)
@return the new color
Ghidra/Features/VersionTracking/src/main/java/ghidra/feature/vt/gui/duallisting/VTDualListingHighlightProvider.java