Some Villagers in the desert are spawning as the Swamp version, even though I am not near a swamp

Those villagers are Savanna villagers!

Swamp Villagers Are Purple-ish.

This happens if half of a village structures generated to another biome, causing the villager to spawn on have a different skin. (On Bedrock Edition only; on Java Edition, this does not work).

Examples: a plains village generating near/in a swamp, causing half/all of the villagers to spawn as swamp villagers.

The screenshot shows a savanna villager, not a swamp villager. A savanna can be seennearby behind it.

I saw no examples of swamp villagers being spawned far from a swamp, so I will close this report as Cannot Reproduce.