I used the white-on-grey icons to avoid having the buttons stand out too much and to use transparency so that the text/covers on the screen would slide under them.
I am not wedded to this choice. For example, I could use the same green up/down icons that are currently used in the folder settings dialog. I have no idea what shade of grey they would become, but those of you with the T68 can tell me.
BTW: this is the sort of thing I am truly bad at (user interface & color choices), so comments are welcome.