Naturally.. there's blue, lavender, paint, partridge, blue partridge, cuckoo and more for starters..
https://www.browneggblueegg.com/Standard.html
https://silkie.org/silkie-colours.html
Grey in Silkies is Silver Partridge.. not all colors are accepted to the standard and are considered project colors.
Not sure if anyone is offering them in Porcelain.
Hope this helps give you some ideas.. if you can dream it, you can do it!
ETA: there may be many in other countries I haven't seen yet as with may large fowl varieties..