Drill bit manufacturers usually stamp the diameter of the bit on the upper part of the shank, but after a while the drill chuck wears the numbers off. This makes it hard for me to choose the bit sizes I need at a glance. To remedy this problem, I dip the shank end of the bits into oil base paint, using a different color paint for each bit. Then I put a dot of paint under each hole of my drill bit holder to correspond with the colors on the bits.
When I ran out of ready mixed paints, I started mixing my own colors. With the help of a master chart that hangs on my bit holder I now can quickly pick the right bit for every job. And even after the paint wears off the side of the shank, a dot of color will remain on the bit’s end.