You can get black Dymo tape from a lot of stationers and just stick it on without printing..
..or, maybe it might even be helpful to indicate routes by printing..?
..I think it comes in 9 and 12 mm widths..
1, It's the Train Man that's dressed as Helga - if that makes feel any better.
2, And here's Captain Sensible trainspotting at Dawlish..
..rock 'n' roll..