I've watched the teardown video for the Rigol DP832. It does appear to be the same hardware as the DP832A. When looking for a firmware, I could only find one file for the DP832 and the DP832A. Therefore, I'm left to assume the DP832 and the DP832A use the exact same firmware. So chances are good the firmware just checks something like serial number to see if it should enable the multicoloured screen and all the available options or if it should turn the options off and show the one coloured screen.
I've been looking at the firmware in a hex editor and looking at the various Blackfin datasheets. I don't think these files are for a Blackfin. I noticed with the link that was posted for the Rigol scopes, they show the model number of the scope right at the beginning of the .GEL files. We don't get that with these firmware files.
When I run the Linux file command on the files though, the bootloader .GEL file shows: hp200 (68010) BSD. I wonder if that's a Motorola 68010 processor in there or if maybe file is mistaken. I know when I look at the application firmware, not the bootloader, I see a pattern every so often (more near the endish). 00h through whatever xxh in a row. First one is at offset 8c and goes to offset 011c. It goes 00h - 90h. Second one starts at 06608c and goes to offset 0660cb. It's 00h - 3Fh but it goes 00 01 02 03 04 05 06 07 08 09 0A 0B 1A FD AE F0 10 11 12 13... There's a whole bunch of them like that. I figure maybe the .GEL file is kind of like an archive or something and these mark the start or end of a file or something? In the middles, there's a whole bunch that don't count very high and they have a little bit of data (maybe 40h bytes or so) before the next set starts.