Change colour and bold text in variable product description text box

Hello

I am trying to change the colour and bold the text on only a few words in the Product Description text box of a variable product in Woocommerce.

From research I believe it’s somewhere in the Customise > Additional CSS setting but can work out how to select the few words I’d like to make bold and a different colour.  

I’m very new to this sort of thing. Can anyone enlighten me please?