If your leaves are coming out green then they will stay green, Red Lotus bulbs will start out red/maroon/brown at the very first sight of a leaf but get better color with age and good nutrients. You can help them color up.
At the defense of the seller they have no way of knowing unless the bulbs are started by them first but then they are very sensitive to ship. Thats why normally you get 8-10 bare bulbs and usually get a mix of greens/reds in the end and you decide which to keep.
Its a 50/50 shot on their part to send a bare bulb and call it a "red one" unless they are from a red mother plant of their own in a tank. The greens IMO are a great looking plant too.