I start every digital image from a picture taken of my hand drawn art. Below is what I used to create the picture above.
Yes, they look nothing alike. So to simplify how I got there, I took pictures along the way.
Here is edit #2. I made this by finding some colors that contrasted well.
For edit 3 I used some kind of filter to pull colors around the edges
Then, I started pressing a lot of buttons until I ended up with the image below
I like this image at this point I felt the center was too green. I applied another filter and came up with this image.
Now, I use multiple apps to transform those colors into this picture