If you do something 'until you are blue in the face', it means you work very hard on it or do it for a long time, but in the end waste your efforts because you are not successful.
Martin argued with his mother until he was blue in the face, but she still made him wash the dishes.
You can walk up and down the high street until you are blue in the face, but you won't find a shop selling leather shoes as cool or as cheap as these!
If something happens 'once in a blue moon' it happens very rarely.
I only eat red meat once in a blue moon these days. You never know what's in your burgers, especially after the horsemeat scandal.
This photo of a Southern cassowary won the first prize in the Nature Single category at this year's World Press Photo Contest. The colourful birds, which are closely related to ostriches, can live for over 60 years and stand about 2m tall.