Changing the page colour

As I understand you want this pattern image changed:

templates/hot_hotel/images/content_bg1.png

That's correct - now I can see where that image is located - can I just open it in Photoshop and change the colour and load it back in? I realised its a png file and so has a transparent background etc....

yes download it first to your computer , edit it in any image editor and return it back like that