I can boot into recovery via grub and the low graphics mode option works but I don't really know what to do from there to fix it so I can use a proper graphics mode. It is usuable now though some colours are missing.
According to wikipedia the Tecra A2 has 16-64 MB DDR RAM Intel graphic adapter. If that is worth anything. In Windows these are driver details listed in the video properties: Intel 82852/82855 GM/GME Graphics Controller.