Tobar said:
Luke's hologram in ROTJ is in color as are the holochess game pieces in ANH and the attack plans on the Deathstar II. The general theme is that all communication holograms are in blue while prerecorded ones are in color. Which is why it has always annoyed me that the attack plans in TPM for the palace are all blue with a single red line.

You are so right! Luke's is in color too, so...if it's a retrieved file is in color, and all real-time comm is bluish? makes sense, real-time comm is much more demanding of network resources than retrieving a pre-saved file hehe. The plans for the palace you are referring to are the blueprints of the structure, maybe they wanted to reinforce the idea that they are blueprints not holo-photos from the palace, and hence generated from an architectural file which are usually monochrome, the red line is the route she is showing. Not to be annoyed by that.