Basic color theory shows that combining red, green and blue lights together gives white light. This also holds true for their complimentary colours, cyan, magenta and yellow. Nick Fancher has an excellent guest post over on the Scott Kelby blog on how a photo by Sølve Sundsbø inspired him to use multiple flash to create a multi shadow effect. Thinking about how colours mix led him to start using gels to create really funky shadow colours. Using 3 flashes, with 3 different gels is the key. The gels are of course the cyan, magenta and yellow we mentioned earlier. Where the 3 overlap, the light is white, but elsewhere, it's the combination of the different gels, or in areas of shadow, the colour of the gel that's filling in that area.That's the thing about using gels, they really work best in areas of shadow. Because the lights mix, they can wash other colours out, so any gel that lights into a shadow area will be at it's purest.For my afternoon of play with Emer from Roza Model agency, I set up my 3 Godox flashes, 2 V850's and 1 V860c. I triggered them all via the FT-16s trigger, which allows you to set the power remotely, as well as trigger the flash. Using MagMod gels and holders, I placed the flashes at roughly 6 inch intervals, powered to 1/64 power initially.As the shoot was for fun and experimentation, I travelled light and used my Fuji X-Pro1 to shoot with. I started without the gels first to get the following shot:I also tried using a Canon T-SE90mm Tilt Shift lens on an EOS-Fuji X adaptor for a few shots. I used the tilt to angle the plane of focus, creating a much shallower depth of field. I also rotated the lens on the mount so it wasn't on a vertical or horizontal plane. Here's one of those shots.For the last set, I went with the gels and spent time moving the flashes around, and swapping the gel positions to get different looks. Here's some shots from the final set.It was great fun and I'll definitely revisit this for an editorial.