Disc labels have never worked well. If the label isn't perfectly placed or if they start to come unstuck it off-balances the disc and you are left with a coaster because it's very difficult to remove the label completely. An off-balance disc could possibly even damage your optical drive.
The best ways to label discs are:
Get a Lightscribe drive and media. This option limits you to b/w labels, and I'm not sure what the state of lightscribe software is for Mac these days... or
Get printable media and a printer that can print directly on the discs.
I know it's not exactly what you asked for, but stick-on disc labels are nothing but trouble in my opinion. I'm sure others will disagree though.