Creating a custom face for a variable shown in global-mode-string?

[Marc Coquand]

I have a indicator I've created which shows if my custom ctrl-lock
should be shown, the state is stored in a variable ctrl-lock-state, I'd
like to turn it red.

I've added the variable to my global-mode-string the following way:

(push '(ctrl-lock-state " [CTRL] " "") global-mode-string)

And it shows up without any issues.

Is there a way to change the color of it, so it is shown in a red and
bold color?

Thanks in advance. 

-- 
Marc