Until I started reading H&H I had only rarely seen perlino, cremelo and such colors. To me the horses look like they border on albinism. When did these colors pop up in breeds like the Connamara?
I don't know. Has palomino always been present in Connemarra ponies? If so, then cremello and perlino would have always been present too. There was probably a time when cremello, perlino and the like would not have been at all acceptable.
Pseudo albino was a name sometimes given to cremello.
The cream gene presumably existed for a long time in the ponies of Connemara prior to the breed becoming a breed.
Once the Connemara society was formed I believe that one of the two foundation stallions to be used to improve and strengthen the breed was a buckskin (dun to Connemara breeders).
Buckskin (dun traditionally) is one copy of the cream gene on a bay horse. Two buckskins need together has a 25 % chance of a double dilute (perlino cremello or smoky cream depending on the horses agouti and extension status) so although I don't think you can use the double dilutes as breeding stock they will crop up. Also as someone has mentioned grey hides a lot.
Our native breeds used to be a lot more colourful before breed registries and showing fashions.