In my job, we draw on grease boards to brief others, formulate our gameplans, and explain what we are going to do… and yes, we typically use all four colors routinely (it’s almost like coloring in kindergarden, only I’ve upgraded from crayons). Since we stand all the time as we do this, we’ll either tape all four pens together or mount them on a piece of wood.
I decided to make my own customized one. All this requires is some small scrap blocks of nice wood from your scrap pile; I even get fancy and laminate up contrasting woods to create stripes. The inset wood (where the pen caps are) are naturally colored to match the pen colors – starting from the blue: Blue Mahoe (found here), Green Kauri (here), Gabon Ebony (here), and Bloodwood (here).
Minus some “electric” help in sanding (because it can be quite monotonous to shape it to your hand) and drilling, the rest was done by hand (mainly insetting the exotic woods) and shaping the block with handplanes. It is sanded to match my grip, making it comfortable to hold and organic looking.