Honestly, they really shouldn't colour the ponds for Open Day. They insist on doing it every year. It looks pretty good on the day, with the little pools of water bright and happy. But then as time passes, they get darker. So now the blue one looks quite unnatural, but in a relatively normal way. The red one looks like some sort of horrible murder has been committed in it. And the yellow one.... er, well... it looks like we've been visited by a flock of incontinent mammals with kidney disease. Ahem. Pond clean-out is in order, I think.