Hi! The first Disney Channel Original movie was Under Wraps, although because you said it had a red and yellow color pallet it might not be that.
There are some DCOMs that feature red and yellow heavily but they were made after VHS were really phased out. (Early 2000s). Some of them are Jump In!, High School Musical, Wendy Wu Homecoming Warrior. It could be possible that your teacher copied those onto a VHS to play to the class though.
The VHS backing for Zenon, Girl of the Century is a hot pink and yellow. Halloweentown also had a warm color pallet with oranges and yellows
While looking it up, I found that some Disney Original Live Action movies were officially released in a VHS case with a red and yellow Walt Disney logo on them. You can find them in this Ebay listing. Here is also a picture of a lot being sold:
If none of these are the ones, can you remember what the movie is about?