Caption slider – change letter colour

is this your active theme?
https://themeforest.net/item/owl-multipurpose-restaurant-cafe-wordpress-theme/20299762

if yes, the I suggest asking your question for color and position of caption in the carousel here:
https://themeforest.net/item/owl-multipurpose-restaurant-cafe-wordpress-theme/20299762/support
to get guidance from theme developer team

Thanks for clarifying the website for the developer of your theme.
https://8degreethemes.com/

I see in the footer area of the website https://8degreethemes.com/
that there is a support documentation link for the themes
https://8degreethemes.com/documentation/

best to get guidance from theme developer’s documentation for changing position and color of the slider (if the slider was included or recommended in the theme package)