you can use the color picker in your editor if you can’t touch code.
But most templates has an specific ID for DIV than contains every page of your content.
You can find the Specific page ID by “view source code”
The, you only need do add this to style.css file on your template
#the_page_DIV_specific_ID { color: #XXYYZZ }
Where XXYYZZ is the Hex color you want to apply.
It will apply the change to ALL elements (headers, paragraphs….) in the whole page (only that page).
But, by the way is easiest use the color picker as you can do in any other text editor, like word, when you’re editing content.