private ColorExpression createResultColor(HiddenTokenAwareTree parentToken, double red, double green, double blue, double alpha1, double alpha2) {
double roundAlpha = roundAlpha(alpha1+alpha2);
if (roundAlpha<ALPHA_MAX-ALPHA_EPSILON)
return new ColorWithAlphaExpression(parentToken, round(red), round(green), round(blue), roundAlpha);
return new ColorExpression(parentToken, round(red), round(green), round(blue));
}