How to change the colour of "Ask a question" button in the Module (Not Component)

Hello,

I know I am asking too many questions..... please bear with me for a couple of days

I installed the "Ask A Question" module and by default it displays the button in green. I would like to change it to "Blue", the same blue which is applied to the "Ask A Question" button in the EasyDiscuss component area (Flatt) theme.

What code do I add to the custom.css?

Regards,
Mangesh