header menu, site title & tagline color / header image question

We're trying out this theme and to make it work I need to solve a few unusual problems. First, to work with the image chosen for the home page I changed the color of the text in the site title, tagline, navigation and the text intended to ride on top of the header image to black. The problem is that if we leave the original image on the other pages (which we may do) the text for the site title, tagline and navigation needs to go back to black. I've been trying to single out the Home page and use the id to only change the text colors on it but thus far have failed. The other issue is that I'm trying to design the layout of the header image to allow for the text which will ride on top of it. Something I am discovering is that the image is sized differently on the page in response to the amount of text added. Weirdly, instead of becoming smaller as more text is added, the more text the larger the image. This makes it difficult to get it right with the image. Some guidance related to this would be helpful. Also, the instructions for the theme don't seem to go with the theme and lack guidance in the form of image sizes for the theme. The website is behind a "coming soon" page but I will take it down to get past this. The url is https://thetendedlight.com I hope we can resolve this quickly so I can hide it again. Thank you