The ultimate test would be to figure out an exbeeriment brulosopher could do where you have a triangle test to see if people could tell the difference between a beer with and without crystal malt added.
Maybe two belgian golden ales. One uses a crystal/caramel malt for color and straight cane sugar to hit gravity. Second beer, same base malt, no specialty malts, and darker candi sugar to reach the same gravity *and* color. This is about as creative as I can be on a way to test two beers against each other in a triangle test, where the color is close, the gravity is similar, the malt bill is the same, but the color is derived from different sources to see if theres a statistical difference (enough people select the odd beer out) and if they can detect the difference.
Or a IPA on the darker side (closer to 15 SRM) but using the same candi sugar in one, and crystal in the other with very simple malt bills in both.