I was having trouble coming up with a topic, until I overheard a strange conversation on the train home from work the other night. A girl was telling her friend how she wanted to get colour contact lenses. Her friend then went on to explain how if you wear them for too long, you will be blind or see everything really brightly for a while after you take them off, and how someone who had to wear them to play a part in a movie went completely blind. This had a definite urban legend ring to it, so I decided to investigate further.
The first thing I found was this Usenet article about an editorial published in Eye and Contact Lens. Although the article talks about coloured lenses, the main problem seems to be that these are over the counter purchases, with no prescription. The problem is that the lenses may not fit right, and cause rubbing. This results in infection and potential blindness.
Eyecare professionals will take careful measurements before prescribing contact lenses, to ensure that these problems do not occur. Buying over the counter contact lenses, coloured or not, is dangerous and can lead to blindness. Getting prescription contact lenses, coloured or not, seems to be fine.
I did discover that the colouring of lenses is an applique, which gives the lens a microscopically less smooth surface than regular lenses, which could potentially cause irritation. Not for the reasons suggested by the girl on the train though.
Also on this page we find the possibility that the coloured part of the lens can potentially enter your field of vision, if the lens moves or the pupil is very dilated. Still nothing about brightness or blindness though.
As for the movie star going blind, I could find no references. Apparently coloured contacts have been used in movies since Audrey Hepburn used them to play a blind women in Wait Until Dark in 1967.