The Image Editing API allows you to easily add a colored outline around the subject of your images.
outline.color
To add a colored outline to the subject of an image, set the outline.color argument to a solid color value. This can be any hexadecimal color code without the # symbol (examples: FF0000, FF0000EE) or a supported color name (see list below).
(original image)
outline.color=white
List of supported color names
aqua
black
blue
cyan
fuchsia
gray
green
lime
magenta
maroon
navy
olive
purple
red
silver
teal
white
yellow
To preserve the background, you must also set removeBackground to false.
If you want to give it a try, here is a code snippet to reproduce the example above: