You can edit any image's opacity and add a background color from an image's toolbar.
Select your image, then select the Opacity icon from the toolbar.
Select a standard color or click + to select a custom color (you can enter a hex code for a brand color here), or reset the background color to transparent.
Use the slider to edit the image's opacity.
At full opacity (with the slider all the way to the right), the background color will not be visible. As you move the slider to the left to reduce opacity, you will see the background color become more vibrant as the image's opacity decreases.