I think the fender hash marks were originally from racing. Basically to tell what team a car belonged to.
For instance, two blue Corvettes, one with red hashes, the other with white.
I also think that Corvettes and Ferraris where the original cars with the fender marks.
99 Chevrolet Camaro Z28 M6 - 6.676 @ 103 in 1/8, 10.512 @ 130.2 on street tires, H/C/I
93 Eagle Talon TSI AWD 5spd - Built 6 Bolt, 16G Evo3, HKS 272 Cams - under construction
94 Mustang GT - 5.0 bored and stroked to 347, Vortech V1 @ 10 PSI, Tremec TKO 600 - PIA