Thanks for the background description, Mark.

I believe that custom draw will work fine, in ooRexx, with one dialog.  Trying to do multiple dialogs with list-views at the same time, is not going to work well.  To do that, you would need to write the application in C / C++.

Well, the funny thing here is that if I only generate one listview it is never coloured, even if it only consists of 2 rows. But if I generate 13 listviews in a tight loop, some of them with 1000's of rows, all but one end up with the correct colouring! So unfortunately this doesn't match your explanation to the problem.