how do i change just one page title's color to white?

You can do that in the CSS code by using the page-id as a CSS selector to target the element that you want to change only on that page. If you want specific help, you’ll need to post a link to the site and page in question.

Okay, try this — add to your CSS:

If you are trying to hide it, this is better than using the same color:

.page-id-265 #content .entry-title {
   display: none;
}