Is there a way to disable blue screen effect on iPad when accessing documents?

I do genealogy using my Ipad Air. Each time I access a document, it turns blue the moment I touch it, making the old handwritten writing hard to read. I have to touch outside the document to get rid of it, but if I need to enlarge it again to read more clearly, it’s blue again. It has done this from day one, and I have checked all settings and tried everything I can think of. Is there a good reason for this feature? Can I stop it?