I have no idea if the color in DuracellEnergizer's second posted image is accurate (my copy of Dark Empire is an older TPB that doesn't include that poster).
However, while trawling the Internet, I did find the cover art for Issue #5 of the series:
Palpatine's clone is wielding a white lightsaber here. Very Ralph McQuarrie. I approve.
It's quite possible therefore that Duracell is right, and the poster in question originally featured an orange saber blade.