My website looks different on different browsers

Does anyone know why the colour behind the text is different in the two images attached? The first is with Safari and the second is with Mozilla. For some unknown reason, I just noticed that the Safari version has lost the colour I initially put in (it is is now inexplicably changed to white) . The irony is that I made the website in Safari. It worked fine for a few months but now has suddenly changed. Any help would be appreciated.