Redscale is done by putting the roll of colour film into the canister with topside and backside reversed. Originally a DYI project Lomo is now selling the reverse film at a premium and Rolli is now manufacturing films with the filter layers reversed also at a premium.
The gel filters are reversed ordered hence the CMY channels are mixed to an approximation
C' = C + Y
M'= M + Y
Y'= .2Y
This example was done by
1) Change RGB positive to colour negative (don't use the grey scale negative).
2) Remix the RGB channels (I don't know it might be better mixing CMY channels
R' = .2R (Y on negative, Blue on positive)
G' = (G + R)/2 (M on negative, Green on positive)
B' = (B + R)/2 (C on negative, Red on positive)
3)Reverse the colour negative back to a positive (at this step you have a chance to change the colour gamma to bring out the yellows and greens)
3)Adjust contrast and brightness curves
If you are using film you could start with a colour negative and skip step 1.
This is my first attempt at faux redscale so it needs some tuning but overall I find real redscale has a creative yawn factor of 8 out of 10 so faux isn't going to be any better. Give me IR film with the filter built in now that would be creative!
Original Photo
