Your comments

Hi Matt,

I can't replicate it. I tried again and I got the correct message. It could be a problem because it goes through a proxy which kicks me out from time to time. 

Martin
I think the problem comes from looking at it on different size screens. On bigger screens it looks very small. It could be an account setting. Let's see what other people think.
In a few of the backlogs (BRC and lloyds) we have themes that are extra functionality and colouring them will makes it easier to browse the backlog. At the moment we manually change the colour for each story. 
I think colouring the whole theme would look better. 
Regarding how it would behave I'm split between 2 options:
1. Once you colour a theme you can't change the individual colour of stories until you remove the colour of the theme.
2. If you change the colour of a story that is in a coloured theme, then the theme will lose it's colour, the rest of the stories will get the theme's colour and the one you just change will keep the colour you chose. 

Hope it makes sense. I'm in the office tomorrow so I can talk to you about it.