"Colours are black, white and various tones of brown; also combinations of black, or brown with white coat"
This quote from the standard issued by the CPC is not very clear, but in "The Portuguese Water Dog"¹ Carla Molinari clearly states that:
"An official statement by the Clube Português de Canicultura sets the quantity of white on a black or brown coat to a maximum of 30%, while areas where white markings are permissible are defined as follows: muzzle, head, neck, chest, front legs, underbelly, rear legs, tip of tail."
By now it is clear that some kinds of markings are not accepted by the FCI standard, whereas the AKC standard sets no limitations regarding this matter. Moreover, Black with Tan Markings and grey are definitely not accepted in the show ring.