In Money Heist Netflix Original, using a mask was compulsion for the robbers. Otherwise cops could have easily identified them. All the robbers wore Dali mask including hostages inside the Spain Royal Mint.
They also wore red jump suit to look similar and making it difficult for cops to differentiate between robbers and hostages. Choosing Dali mask was decision of Professor who planned the whole robbery.
As we know, Money Heist is originally a Spanish crime drama show. Dali is very popular Spanish artist. Red color symbolizes resistance against authority. Due to Dali's popularity in Spain & red color symbol, Professor chose Dali's mask and Red Jump Suit.
This is my opinion. What you think Am I correct?