private int getLastIndexOf(String text, int backwardsIndex, char c) {
		for (int i = backwardsIndex; i >= 0; i--) {
			if (c == text.charAt(i)) {
				return i;
			}
		}
		return -1;
	}
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