If you need to hide the differences between tablets (or capsules, really), like size, shape or color, for a comparison study the answer is to put them all in the same size and shape capsules.
So, today I am helping put little blue tablets into orange capsules. We have a machine that fills this ring-of-holes with capsules, while pulling the body from the cap. Then we sprinkle in a little bit of the filler material (itty-bitty little balls of something. I doubt it's sugar, though, because the medicine is for diabetes) into the bodies. While that is happening, we fill another ring-of-holes with tablets and drop (*ahem* that sounds so easy....) the tablets in the capsules. Fill the capsules the rest of the way with the filler, put the caps on and done.
Takes four people. We managed a little less than 100 rings worth this morning. We are behind. Stupid machine keeps messing up.