Blue Horses???!?

So, I went into a speedrun of the 1.16.5 version of Minecraft java editon and it also was a pretty amazing seed. Then I notice BLUE HORSES. They didn't have heads and their white part faded in and out. the seed is 349465632249901447 and I tried checking on other seeds if they appeared, but the blue horses were only on this seed. All the horses spawned in other locations were normal.