That "LEGO" mug is The Worst Mug Ever!
It claims to be building-brick compatible but the grid spacing is off and most real LEGO don't fit on ANY of the surfaces!.The orientation of the planes is inconsistent, sides of the cup facing user have holes like on the underside of any plate but are too shallow and widely spaced to use and the flat sides make drinking quite difficult. Handle is uncomfortable. Cup is hollow, made from two parts and rattles when placed on table. Not dishwasher safe nor intended for hot liquids!
It is a nice shade of grey and holds markers ok for $7 (including shipping!) but it's a depressing, horrid product.