Wouldn't hurt to take the precaustion of using blue tape. What's the worst that could happen? Nothing. What's the worst that could happen if you don't use the tape. I don't know but are you willing to find out? Blue tape is cheap.
If you use an aniline (alcohol based) dye like Fiebings leather dye (the most commonly used dye by professional pipemakers), there's no need to mask if you don't want to as it wipes off easily with alcohol.
I bought Morgans St Patrick's day Bones CW and thought I asked for a yellow stem but received a green one. Now that I look at it I think I will stain the stumel green. Wish me luck. I'll report on my progress.