Gloss Varnish.

[Paul]

Winsor and Newton Gloss, or a Car bodyshop gloss lacquer.

[Peeler]

Thankyou all, useful ideas. I have several different greens & several different varnishes to hand, so I tried various combinations on spare bases & laid them out to dry, with the green & varnish (or not) duly noted on the back of the base. After giving them due time to dry, I returned to them.
One was even darker, one was far too light, some were good, some were OK. I placed painted figures on them to see how they looked. I ummed and I arrred. I had a cup of tea. I made my choice for my preferred one.

And it was the one what I'd already been using. I'm happy again.

[BaronVonWreckedoften]

Well done, that deserves a pie.

[Shahbahraz]

confirmation bias I say. You should conduct a double-blind trial with randomised volunteers. Though where you would get all those blind volunteers is tricky. I mean, putting up posters doesn't work.

[Buff Orpington]

And I wouldn't put too much faith in their colour perception either.

[grizzlymc]

I know a completely blind kid who can tell the difference between cans of fanta, coke and lemonade from feeling them.

He could also tell the nose of my car from his dad's identical car.

[Purple]

Use your normal varnish and then repaint the entire figure over the top of it

[goat major]

and then varnish it ?

[grizzlymc]

Followed by a repaint with a little white mixed in with every colour, then re varnish again.

[BaronVonWreckedoften]

He could also tell the nose of my car from his dad's identical car.

I told you you should have scraped that poor cyclist off the radiator grill.