Why does Luke have a blue lightsaber post-ROTJ in some early Legends works?

Question

In several different early Expanded Universe works set after Return of the Jedi, Luke is shown or said to use a blue-bladed lightsaber:

Luke whipped out his lightsaber, and its brilliant blue glow cut through the shadows. Dozens of aliens screamed and covered their eyes in pain, and many shouted in dismay as they leaped for the door. A dozen rat people scurried deeper into the shadows to watch the fray with glittering eyes.

_{The Courtship of Princess Leia (1994), page 106-107 of paperback edition; emphasis added}

The humming whine of a lightsaber startled him. He whirled around. The blue light filled every corner of the room and even lit a dust-mouse beneath the bed, as if the light were too powerful to cast shadows.

"Where've you been?"

Luke slouched on the deep couch in the corner, wrapped in his robes, his legs extended. The lightsaber flicked off again, plunging the room into darkness.

_{The Crystal Star (1994), page 114 of paperback edition; emphasis added}

_{Heir to the Empire (1995 comic adaptation)}

In theory, in all of these cases, he should be using the green-bladed lightsaber first seen in Return of the Jedi, and that even seems to be the hilt illustrated for the Heir to the Empire comic. Has it ever been addressed why this choice was made, or if it was just a recurring mistake at the time?

_{Note: The other arguable examples I found are the cover of The Glove of Darth Vader and interior panels from Dark Empire, but they're not included here since neither one has very strong color fidelity in general.}

Answer 1

The lightsaber was originally intended to be blue, but was changed during film production.

From IMDB:

Originally, the color of Luke's new lightsaber was blue, the same as the one he lost in Star Wars: Episode V - The Empire Strikes Back (1980). Luke can even be seen wielding a blue lightsaber in early movie trailers. However, when a scene of Luke assembling and activating his new lightsaber, (still blue), was cut, George Lucas thought the audience might not understand that Luke's new lightsaber was not the same one he lost on Cloud City. To avoid confusion, Lucas decided to change the color from blue to green, making it clear that Luke was using a new light-saber.

The most likely explanation for blue lightsabers appearing in post-ROTJ novels, then, is that these novels were written based off of an earlier version of the ROTJ script where Luke's second lightsaber (the one he built himself) was still blue, and this was either not caught during the editing process and/or went to print before the final film script revision.

You yourself mentioned that this only appears in very early post-ROTJ Legends works. This is presumably because later works used the final ROTJ script that had Luke consistently using a green lightsaber.