Photoshopping background and multiple photos in 1?

I was wondering if I had a white background am i able to transform it into different colors like this ppicture for example? Right now I'm using GIMP also how would I make the more more vivid in color like kind of dark but vivid

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how would i make the photo more vidid and clear in color
like this one

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also i see some photos they have multiple photos in 1 photo and its divide up llike comic strip is that a program feature?

1) You can make the backdrop that way by the way you light it. You can put colored gels over the lights when lighting the backdrop.

2) This photo was taken with:
-Long exposure
-High ISO's
-Studio lighting
That's how you can get detail in the sky at night (long exposure/high ISO's) and detail in the portrait (fill light from studio lighting)