@Override
	public Color getBackgroundColor(BigInteger index) {
		Color primaryColor = primaryModel.getBackgroundColor(index);
		Color secondaryColor = secondaryModel.getBackgroundColor(index);
		if (primaryColor.equals(primaryModel.getDefaultBackgroundColor())) {
			return secondaryColor;
		}
		if (secondaryColor.equals(secondaryModel.getDefaultBackgroundColor())) {
			return primaryColor;
		}
		return blend(primaryColor, secondaryColor);
	}
Class for blending two {@link ListingBackgroundColorModel}s.  If neither model has a color
different from its default, then the primary's color is returned.  If only one model
has a color different from its default, then that color is returned.  If they both have
colors different, the color returned is a blend of the two colors.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/codebrowser/LayeredColorModel.java