Again, I can only give you XR info but I'd be surprised if the Dommie was vastly different.
The workshop manual says "install the piston rings with the marks facing up" - so if you can see any marks on them follow that.
The oil ring is the one that comes in kit form and that's fitted in the third slot down from the top. The other two plain rings are differentiated in the book as follows -
top ring - has an "N" stamped next to the gap and the outer edge is beveled very slightly both top and bottom.
middle ring - no marks shown but the outer edge is angled with the wider bit going at the bottom.
It might help having a closer look at them with a magnifying glass or something and seeing if you can spot the difference.
It doesn't give any info on colour or anything else.