The application of the dye in small biopsies for color marking should be very precise. Although the wooden applicator can be sufficient, I use more and more the StrataTips, .17mm PipetTip (STARATAGENE, Catalog # 41005) as a device for dye application. The plastic tip with a smooth, un-wettable surface allows the user to apply the definite amount of the dye at the precise place.
Cleaned with a paper towels, the tip is reusable and lasts for a long time. A pinpoint cutting edge can be shaped for especially precise applications of the dye that sometimes is necessary in small biopsies for correct orientation. A wooden handle might be added to make the tip more convenient. Of course, there could be different kind of applicators, but the the principle of a plastic, washable, and sharp edged gadget would be most beneficial for ink application in biopsies.
I use this gadget more and more for monocolor dye application in small biopsies including skin biopsies. It seems that a standard wooden applicator is more suitable for multicolor applications when a larger surface is covered.