My favorite cardstock for coloring with markers, pencils, and inks of many types is Spectrum Noir Ultra Smooth White Cardstock 100LB weight. It is strong enough to hold up to fussy cutting or diecutting. It is very smooth and bright white which helps your coloring to pop out from the paper. Colors remain vivid and the typical bleed through is less than with many other types of card stock. I love working on this cardstock for all types of stamping and coloring projects. Below is a sample of my current project using Heartfelt Creations Tropical Paradise Collection. I colored this parrot with the Zig Brushable water based markers and the paper held up really well. Most card stock starts piling quite easily with water based markers but this paper stood up through even a second coat with no issues. I'm not the best colorist. Having a quality paper to work with really makes the job much easier. I don't sell this cardstock myself but I will leave the amazon link below so that you can find it for yourself.
Link to Spectrum Noir Ultr Smooth Premium White Cardstock on Amazon amzn.to/2ovd0yw
I'll be back with more project shares with this fun and colorful collection.