In my search for a perfect version of Thomas The Tank Engine & Friends/The Railway Series, I have thought about making Henry the Green Engine and Percy the Small Engine out to be female engines. To tell you the truth, I had always head-canoned them as female since I was a wee lad because I thought the color green was a very feminine color representing Mother Nature. Duck and Oliver being the balance, I never really bought into Henry and Percy as being male.
For Percy, there's a little bit of logic that I'm getting at. Since one of now her prototypes was named Trojan, Percy is short for Persephone - Hades' wife from classic Greek Mythology, which Sir Topham Hatt (the Fat Controller) would give to the engine before bringing her to Sodor. What do you think, guys?