That sounds like a promising candidate, but I'll first try convincing my specialist diabetes nurses that I could do with a "backup" pen that just happens to be red. I'll probably only succeed in annoying them however, and not get the spare at all, or just end up with yet another blue one. 😉Could you wrap washi tape around the body of the pen (whether they're disposable pens or reusable pens)?
It's easy to find washi tape in patterns or solid colours, and in different widths. It would also be easy to remove the tape if you find a more permanent solution. The tape is papery and doesn't leave a residue in my experience.
I'm on a pump but carry Abasaglar with me when I travel, and when the pens are nearing expiry. To avoid mistakes, I secure the cap to the body of the pen with washi tape so I don't use it without thinking. It's easy to remove the tape if I do need it, but I'd need to remove it intentionally - the tape doesn't come off on its own, even when loose in my diabetes bag.
I tend to leave my basal at home when i go out, but carry my active fast acting pen around with me for "emergencies", so there shouldn't be too high a likelihood of mixing them up. I am getting a bit on the old side nowadays however and the biggest risk is in the pre-breakfast injections, when i normally have both my basal and fast acting. Getting the doses for the two mixed up, as you will know, is not going to end too well.