C++ (Qt)
//Цвета по умолчанию...
QColor base = QColor::fromRgb(203, 203, 203);
QColor color1 = QColor::fromRgb(153, 153, 153);
//QColor color2 = ...
//QColor color3 = ...
 
double delta1 = color1.valueF() / base.valueF();
double delta2 = color2.valueF() / base.valueF();
double delta3 = color3.valueF() / base.valueF();
//...
 
QColor newBase = QColor::fromRgb(240, 240, 180);
 
//Рассчитываем новые на основе newBase
QColor newColor1 = QColor::fromHsvF(newBase.hueF(), newBase.saturationF(), std::min(newBase.valueF() * delta1, 1.0));
QColor newColor2 = QColor::fromHsvF(newBase.hueF(), newBase.saturationF(), std::min(newBase.valueF() * delta2, 1.0));
QColor newColor3 = QColor::fromHsvF(newBase.hueF(), newBase.saturationF(), std::min(newBase.valueF() * delta3, 1.0));