Orange?
Orange is the whitest color of red, so that picture is taken at night it should have been even dark-reder instead of orange.
When I first saw the movie I thought it's orange and sometimes it's transforming to red in some cases.
Teoreticaly it's impossible to say unless the director Simon Wells could tell us.
The color change is because of the ambience. Same you could say with Balto fur being black or grey or Jenna bottom fur, being white or white-redish sometimes.
Same think was with The Secret of NIMH where they were talking about Ms. Brisbys manta. Producers said they used about 40 combinations of color around the red spectrum that difference with the light for perfect ambience.