[Gordian Blade]

"white, to yellow, to orange" -- sounds suspiciously like something going through the black-body spectrum as it cools down, like a hot piece of iron in a blacksmith's fire. That would be consistent with some piece(s) of junk entering the atmosphere. If the words, "to red," were added, that would clinch it in my mind.

[linemann]

good point

[SEVENCROSS]

There was some red, it was so colorful the kids said it looked like fireworks, and it did look like pieces burned out or trailed off, and others would flare up and change colors.

[Turk2]

The direction of motion also seems to imply a deorbiting satellite or space junk (which is mostly left-over stages from launch vehicles or old satellites just left in orbit to be deorbited naturally by atmospheric drag). Good call on the color change by the way.