Yeah, coloring or not from the original, I don't think it was ever meant to be the Executor. As an editor, there is too much evidence that this is supposed to be a regular SD. If it were ever shot as a blue tower, then it is extremely likely the original intent was for it to be the Executor BUT as editing went along they ditched the original intent and used the shot to show a bridge conning tower of a regular SD.

It's been done several times in this film. Just look at the setup of the Rebels on Hoth as they prepare their rifles. The blaster cannons behind them were already on fire before the battle even began. Or when Han peeks up to look at the probe droid. The snow in front of him already had debris from the probe droid.

These examples show that is was common on this show to use shots out of its original intended context and placed elsewhere regardless of small continuity errors. As an editor myself, it makes zero sense narratively to place the Executor tower at that point. If it were to be a 'fin in the water' type thing then it was done very poorly in an otherwise brilliant lead up to the reveal of the Executor. I think in this instance it'd be wiser to forego the blue and keep the coloring more in line with that of a regular SD.

Just my two cents. Fortunately for me, if I don't like it the way it ends up I can just change it to suit my own wants. I did that with ANH:R and I suggest anyone else do the same for themselves. It's not that hard to change a few little things if you really want to.