Sometimes it’s the little or simple things during moments of action that can cause annoyance or unintended consequences. One of those things, in my experience, was the panel arrangement/design of pull knobs for diff lock and 4WD. The panel can have up to three knobs, all identical, and therein lies the annoyance. Having only one knob is not a problem, obviously. My Syncro has two knobs (me not included, I hope in writing this tale of woe). So, in a moment of necessary quick action which identical knob do I pull? - left or right? My little grey cells suddenly become flummoxed as I drop my peepers down and across to select the correct knob in all the excitement of traversing the rugged terrain ahead. My high school history teacher taught me: repetition facilitates recall. Selecting a panel knob is not an everyday occurrence. Now, it’s taken me some writing here to get to what I’ve done to solve my annoyance and, here it is: the 4WD (decoupler) knob is now a shiny chrome knob and the diff lock knob remains black original. And, what about a third knob (if you have such), well, that’s your problem to deal with.
Oh dear!! I hope you did not pull the wrong knob leaving you stranded… I had never thought about marking them, but am used to referencing the symbol above the knobs to identify each. Hope the shiny chrome knob helps next time 
The shiny chrome knob works well for me and, there’s more knobbing - my heater slide levers are all identical and black. Yes, I think you may have guessed it; the heat slider lever has a red cap on it! Idiosyncratic - probably, but I do love my Syncro.
Good idea! On the vans fitted with a front diff, whilst the knob isn’t a different colour, there is a mechanism that requires a twist before being able to pull it out. Suppose the consequences of accidently getting the knobs mixed up and pulling that particular one are greater than most.