What most people seem to forget utterly is that Mara Jade actually uses a blue lightsaber. At the end of The Last Command, Luke gives her his old weapon as a gift, and in Vision of the Future she is stated to still be using the same one.

Since VotF is the grand finale of the Star Wars story (I do not acknowledge the existence of virtually anything that follows), it can be asserted that she still uses the lightsaber that once belonged to Luke's father.

Works that portray her time as the Emperor's Hand do show her using a magenta lightsaber, but following her master's death she did not possess this weapon any longer. Anything showing her with this blade color that is not of that time period is a continuity error. It's not altogether surprising that these details are overlooked, since most artwork tends to show her in leather catsuit type outfits, but if you actually bother to read you'll easily discover that this bears no resemblance whatsoever to Zahn's descriptions of her.