headings custom

Hello !
I’m playing a lot with your slider here :
https://www.ceri-bois.fr
And it’s so awesome !

Just one thing :
I couldn’t find how to use the H1, H2 etc headings AND custom their color at the same time.

for example, if i put my text as following :
<h1> my heading</h1>

(it will display in gray, wich is curious because my custom theme is set to display texts in white. But nevermind)
Then I have set a
color:#fff;

command in the custom css … but it doesn’t affect my text.
any tip I’m missing ?

https://www.ads-software.com/plugins/crelly-slider/