Changing colour of title text only on template testimonial page

Can anyone help. I have used a custom testimonial template but wanted to change the title only to white text but it doesn't allow me to do that.  Do you know how and where i can enter a code to make this happen?

Can I alter the size of the header as well?  I am looking at the bottom of the About Page

My website is https://www.3cscopywriting.com/about

Hi,

Which text? Can you take a screenshot?