make subject pop?

[echoes]

I have various photos that are watercolor/marker---each photo is mostly a bland white with a color subject. 
I'd like to:

1. convert the bland white background to #ffffff OR transparent
2. make the subject colors more intense

I have several photos, so ideally I do *not* want to manually edit out the subject with the selection tool. 

Any suggestions? 

Here's a sample photo: https://ibb.co/F0RQ9Cd

(Note that the colors here are really bad, adding a sample photo just for illustration.)