Background for store and products pages on Dawn Theme

[AuthorAngel]

Hi I am having trouble getting my store page and each product page to have the theme colours I have set up for the remainder of my website. It needs to be black background with the grey writing but even when I select that choice on all my templates it just won't stay. Could anyone help please? 

Website  is:  lesley-jones-writes.myshopify.com  and password is help.

Thank you

[nick404]

you can try applying with custom CSS

[AuthorAngel]

Thanks Nick404 but how do I do that? I'm still new to Shopify