Is there a way to stop the new unity feature that changes the colour of the launcher and notifications that matches them to the wallpaper?
Its an interesting feature, but I would rather not have a yellow or brown launcher just because the wallpaper has some yellow or brown in the image, its pretty ugly.
The chameleon effect can be removed from the notifications but it is quite an involved process involving installing an older version of the notify-osd package, a comprehensive guide can be found here: https://askubuntu.com/a/128508/40955 then the notifications will be the same dark colour as they were in 11.10 (or you can choose a custom colour)
The instructions below currently do not work, due to Bug #975350
You can force the launcher to stay one colour and not change to imitate the wallpaper colour by installing the MyUnity tweaking tool from the Ubuntu Software Centre.
When installed navigate to the Launcher tab and click the color bar
Select your preferred colour from the colour wheel and the launcher will remain that colour no matter what the wallpaper colour is.
