I have three Pennsylvania steamers: Lionel Legacy M1b, MTH Premier Atlantic, and the MTH K4 Pacific. They all have the same color on the cab and tender roof.
I have never seen an O Gauge Pennsy steamer with anything but the same color on the cab and tender roof.
I don’t know if the pic Chris (the OP) posted, with brown on the cab roof, and orange on the tender roof is prototypical or not on the real engines, but I don’t think it’s what we are used to in O Gauge.
Chris the OP’s Lionel Atlantic:
My locos:
Lionel Legacy M1b:
MTH Premier K4 Pacific:
MTH Premier Atlantic: