[Helder Crespo]

Thank you all for your tips and advice.
Since I'll be painting the whole mask, doing colour matching on the spot is not feasible for me, as I don't have another mask to serve as guide. Also, and even though matt finishes can be quite forgiving, my painting skills are rather basic, so I'm really aiming at a single spray can solution. The can I already have is really high quality (1K acrylic), bar the colour difference. I've done a couple of tests on flexible substrates to check the paint's flexibility, and I believe it works very well (two thin coats). I don't think B&Q makes custom aerosols, but I may visit the nearest branch with my mask to find the best match and hopefully a standard reference that will enable me to order the ready to use can elsewhere. Duck egg green/blue does seem close on the screen, but so did British standard eau-de-nil, and since paint from different manufacturers can differ quite a lot (even if the paint name is the same), I believe I'll only use the paint general designation as a rough guide to find a more universal code/reference.
My plan is then to strip the mask of its original paint, which should result in a smooth surface, and respray it.
Helder