Spaceclam,
The point Minnflyer and others are trying to make is, the only reason your rich run is pink, is because your FUEL is pink. Other fuels can be green, or blue, or clear, so they CAN NOT result in any pink in the exhaust. Telling someone that pink is good is misleading because it's only true when using certain fuels.

And yes, black is not the color you want to see in your exhaust residue because it generally means metal components are wearing, but again, telling someone that they should buy a new engine just because they see some black residue is wrong, and misleading.

The general impression of your advice is good, just try to exaggerate less, and be careful of your 'facts'.
Dennis-