Blue axolotl don't spawn rarely

Blue axolotl have chance that didn't get spawned its hard to spawn any axolotl.

It does not spawn blue axolotl. I don't think how i keep spawning it but its still regular type..

 

Reproduce:

1. Get the axolotl spawn egg/bucket in creative mode
2. Spawn them repeatedly
3. It shown 4 color types (e.g. Pink, Brown, Cyan and Gold)

These axolotl have no chance to spawn blue by using axolotl bucket/spawn egg.

(Testing purpose: may its intended or not)