How to change back ground color of an image?

Too many varibles ,but I'll give it a try. are there any layers? does the background layer ( the one called background at the bottom of the list in the LAyers palettte) have anything in it? area all the visible layers above the "background" transparent where they are "white"? If this is the case it's much easier than if any of the layers are "white" or some other color- then you need to select out the items you want not to change color, using any number of the available "selection" tools, from the area you want to change color- now that can be a challenge.

To change the background color or an image, you can use Photoshop. Follow the steps below to change photo background color.

Step 1: After running Photoshop on your computer, press Ctrl + O to open the photo you want to edit. When you have opened your photo in Photoshop, right-click on the Object Selection Tool from the toolbar on the left.

Step 2: Select "Quick Selection Tool," then tap "Select Subject" in the upper toolbar to outline the subject in the foreground.

Step 3: Press the "Q" key on the keyboard to enable Quick Mask mode. In this way, areas that have been captured as part of the background will be red. You can zoom in the photo to refine the edges and details to make it captured more accurately. After finishing the task, you can zoom out and tap "Q" again to exit Quick Mask mode.

Step 4: It should be noted that the selected shade will initially color the subject instead of the background. You can press Ctrl + I to invert a layer mask. Finally, just double-click on the solid color thumbnail under the "Layers" tab, and select the color for the background.

If you think the steps are too complicated in Photoshop, you can learn some methods to change photo background color automatically with smart algorithm: How to Change Background Color of Photo?