Named colors are not taken in acount in the button macro

[raphj]

Describe the bug

{{button color="blue"/}} doesn't make the button blue

Steps to reproduce

1. Add the button macro with the wysiwyg editor
2. Type blue for the color
3. Notice that the blue color is indeed picked up by the parameter picker

Expected behavior

The blue parameter results in a blue button

Actual behavior

The button remains uncolored