I don't think I'd want to eat these, they're too beautiful! And quite small and probably slimy. They change colour as they mature from the green that you see here to a bright yellow - they look particularly good at the in-between stage. That's a good question about the colour- quite a lot of the waxcaps are very colourful but they're not usually poisonous. They're quite rare in the UK as they tend to only grow on undisturbed soil that hasn't been fertilised - graveyards are a good place to spot them!