First, if you are looking for color, you are most likely looking for x hybridus or the oriental hybrids. In my area, one does not need to rely on mail order (scores of retail nurseries that operate year round), so I suggest buying when the plants are in flower to get the color you want. Most are going to be sold as seed strains and will contain the potential for a variety of colors, but if you want a specific red or a slate blue for example, you may have better results if you buy them in flower. There are also a few color series (the 'Lady' series, for example), but I have not found many of them to offer the intensity or trueness of color I was looking for.

I also recommend not buying smaller than a gallon sized pot if you want immediate impact - smaller plants may be more of a cost savings but you will wait a couple of years for blossoms, generally. Gallons of the Royal Heritage strain here will run about $13-14, doubles $25-30 and specific colored strains, $16-18 per gallon. These are west coast prices.

I'm sure one can get some wonderful hellebores by mail order - I've just not found it necessary due to the many year-round nurseries in my area. I would think that shipping times would be tapering off for a good many of them now and February or March might be too early for many of them to have resumed shipping. So you might be forced to buying hellebores out of season - not really a problem other than you will have to wait to see what flower colors you have received.