Sandra has a great review of the Squared Moleskine notebook: Life Imitates Doodles: Bleedthrumanade in Moleskine & Review of the Moleskine Squared Notebook.
She used the way the markers bled through the page to provide two ways to use the same color base:
“Got lemons, make lemonade. Got marker bleed-thru? Make bleedthrumanade.”