On this video tutorial Aaron Nace from Phlearn demonstrates how to add (or change) a colored background to an image using Photoshop.
This one is pretty straightforward. You have an image but for whatever reason you want to change the background to a different color. The first stage will be to cut your subject or subjects out, this is probably the hardest part (especially if you have a complex subject) – we have a large number of videos on this subject which can help you with that.
Basically after making a rough selection of the subject in a photo, use the “Select and Mask” tool to refine the edge of the selection.
Once the hard work of cutting your subject out of the image you have many options, you can add another photo as the background or a simple colored background to simulate a studio photo. If you go for the second option choose >Layer>New Fill Layer and pick a color. Place this layer below the layer with the subject and the new color will appear behind the subject.
To add a bit of realism, add a vignette to the borders of the photo by going to >Layer> New Adjustment Layer> Hue/Saturation. Lower the lightness and saturation then use the elliptical marquee selection tool to create a selection around the center of the image and fill the selection with black. To make the vignette more realistic, add a gaussian blur to the layer mask.