While I have used the resistor color code trick with some rifling files I have, I have far too many Allen wrenches to consider doing what you suggest. Why heat-shrink? Go to the local model supply shop and get those tiny bottles of paint in resistor colors, ten disposable brushes, sit down with a mountain of Allen wrenches and stripe away.

I have the wrenches arrayed by size in a block of wood. The Mark I eyeball will usually get me within a wrench or two of the correct size.

You may find it useful to make a copy of my chart...

http://www.homemadetools.net/forum/h...ze-chart-60179

for your shop.