A dark green gel effect nail varnish from Barry M.
Barry M is one of my favourite nail varnish brands, but for some reason or another I haven't bought anything from them in a long time. I think Watermelon from their Gelly Hi-Shine range is my most recent purchase, and I haven't used it much because I forget I have it.
The Gelly range is supposed to be like an 'at-home gel manicure' due to the high amount of shine you get when you apply these colours. They don't claim to last longer than ordinary polishes though, but I do find they last well. The only shade I own is Watermelon so I can't speak for other shades, but I do think this one is very shiny, which hopefully you can see in the photos.
Watermelon is a dark green, fairly similar to that of the outside of a watermelon, but I find I can sometimes see some dark teal in it depending on the light. It's a bit of an unusual colour for me to wear, but I like it a lot and I plan to wear it more often now I've rediscovered it.
I used Sally Hansen Diamond Strength as my base coat, two layers of Watermelon (you don't need two though it's pretty opaque), and a top coat of Revlon Gel Envy Diamond top coat.
The Gelly Hi-Shine range is £3.99, which is £1 more than their ordinary polishes. That's still so cheap though!