The gym leader is in the fuchsia city gym. Its not koga its his daughter janine because koga is part of the elite four now.
just defeat blue, the 8th gym leader
In fuchsia city.
It's south of Fuchsia City.
In her Gym
The tower
Blue is the guy you go to if you want to find the viridean gym leader
You get it from the safari zone warden in fuchsia city after you give him his gold teeth.
you go across route 44
The warden in fuchsia city gives you Strength after giving his gold teeth back.
Mahogany Town. East of Ecruteak City.
The Safari Zone Warden, in his house in the southern part of Fuchsia City.
Vermillion, Saffron, Cerulean, Celadon, Fuchsia, Pewter, Cinnabar, Viridian