I know it isn't a summery colour but I just love Revlon's Moon Candy range of nail polish. There are lots of colours but this is the only one I have tried so far.
The effect of the second application is really beautiful and one that you will want to stare at for hours looking at the way they glint and shine in the light.
Yet as always there are downfalls with such beautiful nail polishes. I don't think it lasts as long as some nail polishes, however if you make sure to put a good quality base and top coat on then it should stay a reasonable amount of time.
Also the second layer to apply leaves the nails with a very bizarre and not altogether pleasant texture to it, however a top coat does somewhat alleviate this problem.
For buying my beauty products I often use the website Feel Unique
Base Coat: SpaRitual
Nail Polish: Revlon Moon Candy in the shade Galactic
Top Coat: Dior