Palpatine got you fooled too. His mastery of the Dark Side provided the illusion of what he always looked like.
Here is one clue. Sith lords can always be identified by their glowing yellow eyes. Tell me. When did you and everyone else first see Palpatine's eyes glow yellow in Episodes I, II and III?
Remember he was
always a Sith and hid in broad daylight.
Sith eyes are when the person is drawing deeply on the dark side. Anakin (Lord Vader), Palpatine, Maul, etc...would not always have Sith eyes. It would be when they are fully immersed in the dark side. This is why Anakin had the Sith eyes for the first time - that we could see on camera, who knows what happened during Order 66 - when he was killing Nute Gunray...a guy he hated a lot because he tried to kill Padme...several times...and the attempted public execution in Episode 2. It's why Anakin's eyes were not Sith red when fighting Obi-wan - he loved Obi-wan, he was unbalanced and not completely Sith - but once Obi-wan chopped off his limbs, he drew deeply on the dark side and said, "I hate you!!!"...and his eyes turned Sith yellow
Dooku was more of a political idealist than one who drew deeply on the dark side and yet during both duels with Anakin, we never see Sith eyes from Dooku. During the animated Clone Wars series, I recall seeing him with Sith eyes during intense duels.
But more on topic, Palpatine muted his force ability around the Jedi, but it would have been a monumental feat to use the dark side to fool every Jedi for 13 years as to his true visage. Yes, the Dark Side is hard to see, but I don't believe that's because Palpatine can cause optical illusions without them knowing they are being manipulated by the dark side.