Susbtitle CSS color

I can’t change the color (grey at this moment) of my NewsLetter susbtitle from the “styling setting” dash.

https://gyazo.com/ddcb4cab22418818dc0896857d9c8d17

Can you give me a css code in order to to that pls ?

Here is my website : https://locationvoiture.touracancun.com/

Cheers
Chris