Can you describe the enhancement? Was it done to make the color deeper or more of one shade or another?
I think this has been common with japanese stones for a while, but sometimes it's just done verbally there (yellow's worth more than green, green's worth more than gray, so light green becomes yellow and light gray becomes "greenish tint").
Wet/dry or oiled/not-oiled will make a substantial difference in color quite often.
You may or may not know it, but I have a serious thing for stones and a lot of experience with what's valuable and what's not (both buying and selling (natural stones), US stones, UK type stones and I've probably sold well over 100 japanese stones). Based on what you mentioned, both of those color adjustments sound to me like they were done to make the stone look more valuable than it is (not saying anything about their performance).
A bone/yellow colored washita that has a waxy look is very desirable, as is a vivid green charnley (I realize you guys can get good charns on the ground in the UK pretty cheaply, but we can't get them here. You can chance across $4 washita stones over here, too, but once they hit ebay, they're not $4).