After much agonizing over my dilemma about what to do with the unit markings for my Tactical Squads, I decided to (as suggested by several fellow hobbyists) apply the GW White arrows provided in the tactical squad box and then paint over them with red paint (Mechrite Red). Following another suggestion, I cut the decals right along the lines in order to eliminate [or minimize wrinkles] and applied the decals using Micro Sol and water. Once the decals were dry, I applied another coat of matte sealer. After the model was completely dry, I used the decal as a guide to paint the red tactical arrow.
The pics above also illustrate the poor quality [at least in my opinion] of GWs Chaos Black spray paint. It causes a noticeable pitting to occur in the model. For a much, much smoother and quick drying primer, I highly recommend Krylon Flat Black Primer, which goes on very light and dries in minutes.