If it doesn't have to be flat like the photo, I would try a center spot of yellow or orange, whichever the center is, (I'm color-blind). Then do a vortex marble using the spot as the center of the vortex. It's hard for me to do a flat surface inside a marble. I did make a wig-wag flat surface inside a marble several years ago. I'll see if I can find the photo and the tut that I used.
Here's the marble. Now to see if I can find the tutorial.