Modify letter size

Hi,
I want to modify the letter size for my website:
https://si3.photorapide.com/invites/photos/2022/11/15vnxq.jpg
to make the phrase’ letters ” All over the world” smaller,
When I modify the size from H1 to H3,
https://si3.photorapide.com/invites/photos/2022/11/152v24.jpg
The letter’s size doesn’t change, but the color changed,
Please tell me how to do so that I could make the size smaller, and not change the color.
thank you so much !