According to Overload (author of Super Sleuth):


From my lists these games uses Direct Color Mode

ActRaiser 2, Romance of the 3 Kingdoms 2, Aerobiz, Aerobiz SuperSonic, Secret of Mana

I know Secret of Mana is a world map (and you'll spend longer getting to that point than you will on the bug itself!)

According to my notes (which may not reflect newer findings):
the palette entry itself (0-255) takes the form bbgggrrr and the tilemap palette selection becomes bgr. The palette index supplies the top bits, palette select the next bit, and the rest are 0. (That is, blue = iit00, green/red are iiit0, where t is the palette selection in the tilemap, and the other is the palette index taken from the tile)

Does that match your documents?