Choose your image then open it up in photoshop. Duplicate your Layer (meaning just drag what I have highlighted and drag it to the small box thats also highlighted.)
Once you have duplicated your layer, click Image Adjustments, Levels.
When you have done that this Levels box will appear. Change the Channel to Red and Change the OutPut Levels to 0, then click O.K
This is how your image will look after you have clicked O.K.
Click the eye so that you can see the bottom layer and so you don't get confused about what you are doing to which layer. So click the eye that next to your blue image. And make sure you click background copy, this is so you've selected it so you can edit it.
Again this is simple. You are doing what you just did to the top layer. So click Image, Adjustments, Levels.
This Levels box will appear. This time change the channel to green and the OutPut Levels to 0 then change it again to Blue. Then Click OK. Your probably wondering why should i do this? Has it actually done anything, well your not the only one. I did. :D
But it does change and clicking OK is only saying I'm finished changing the levels and you can close this box.
This is what your image should look like after you clicking OK. Make sure you click the Eye back on so both Layers are visible.
On the Levels box when you have your images both completed after changing the Levels. Click the drop box where it says 'Normal' above your Layers and change it to Screen.
This is how its meant to look after you've changed it. Click the move the tool and slightly move your image down and to the right and you will see some red and blue appearing though the image. You will notice its 3D get your glasses out and have a look at what you have done.
:D