I thought that Lycoming engines were Gray............
I suppose you can paint yours any color you want!
Lycoming built a bunch of engines for Cessna that were Blue. May have been some of the 76 Series Engines. (76 Series includes the O-320-H2AD engine)
The blue is simply a colour code to say you have nitrided cylinders.
eci.aero/pdf/92-7-1.pdf