Just print bottom-up (the bridges are small but if you want to make sure they look even - set the bridge angle to 45 degrees. You can also change the filament color on layer right after printing the marble. The only tricky part is the marble - make sure you have good first layer adhesion.
PS. I know - there's a lot of strining on my photo (wet PETG) but it still works :)
The author marked this model as their own original creation.