Frogs' knowledge

I must admit, I've never had much knowledge about frogs. Today, during a little break in Amsterdam I saw these ones: very little, very beautiful (I also saw mice, but I did not think it was worth to make a photograph). I automatically liked both, the blue one (what a impressive colour!) and the yellow/black one as well. They looked so special...
Then I read under it: 'poisoneus'. WOW, what a meaning. No matter how much you like them, they can hurt you any time.
How adecuate to have a frog lesson today!!