Normally we don't accept the theoretical of "a registry accepts all colors" as sufficient evidence, but since 1) as you stated, the CDE Sporthorse accepts Thoroughbred outcrossing which could realisitically introduce overo into it's studbook, and 2) you took the time and effort to actually reach out to the studbook, I'm going to accept overo. And the two appaloosas are lovely. Both colors are accepted, thank you for your research
One more note on color - 'sabino' is a term usually used to describe the white spotting family of genes. True sabino - SB1 - needs to be proven with a genetics lab test. This breed can still be sabino in color, they just (more than likely) carry White Spotting or W instead of Sabino/SB1.
Other than that, this breed is accepted. I am adding it to the system now
I am going to accept this breed; however, I am struggling to find information on this breed from reputable sources, and every source I have found has stated that only chestnut horses are considered for addition into the studbook. I'm also unable to find clear rules about their outcross rules, however it does seem that they allow Arabian, Anglo-Arabian and Thoroughbred outcrossing so I have allowed that. All other information accepted, and they will be fully added in the next few days