I honestly think that the jeepneys were cooler before and more colorful than they are now.
If I am right, it was actually started by Jack's Rice and the rest of the restaurant owners followed suit. Here is a story about Jack's Rice https://unlimitedgrubgrabs.wordpress.com/2011/01/12/episode-20-memories-of-baguio-part-2-the-legend-of-jacks-rice/.
Jack Dulnuan, owner of Jack's Restaurant, had the idea to put a little bit of everything in one plate instead of having everything on the table that he will not be eating anyway.