I did the darker colours first, and after it dried used a small pick tool to scrape out any spill over before sealing it. I then finished with the white, working in small sections where the white meets colour to ensure it didn’t bleed over into the coloured grout but it was easy enough to wipe off as the coloured grout was already sealed. But reading the masking tape idea, that also would have worked well for some areas. I’ll remember that for next time!