Ooh, those are the best! They're great for writing, but I wouldn't suggest you use them to color anything in, unless you're crosshatching or something like that.
I say that this is good advice.
If you want to color stuff in, you'll want to draw whatever you want with a pencil, then ink it in and color it. If your work doesn't look totally consistent, then that makes it more original.
A good pen for bullet journaling (or anything for that matter) is a...