We used to have some of those. I believe the Cobalt RaQ 550 is MIPS-based. I am not sure there is a version of Centos that runs on MIPS processors.
RaQ550 uses PentiumIII Should run CentOS, but the BIOS ROM may give trouble
If you do find an answer to this, please share it with the list. I would love to resurrect some of those boxes with Centos and BlueQuartz!
Gerald