We've talked a lot about getting great colour out of your photos, but if you don't like the colour you have, you're not necessarily stuck with it. Here are two ways to change the colour of anything in your photo.
The video above describes two techniques for changing colour in your photos with Photoshop. The first involves using the colour replacement tool/brush to effectively paint on a new colour, and the second involves the more complicated method of manually selecting the object and manipulating it's light and colour values.
Using the Colour Replacement Tool
The colour replacement tool hides underneath the traditional brush in Photoshop. It's the easiest way to replace a colour in a photo, so when it works, it's definitely the best way to go. All you have to do is select the colour you want and paint over the colour you want to replace.
One of the neat features of the colour replacement tool is edge detection, so you can paint more freely without worrying about colouring outside the lines. However, if your brush is too big you're going to find that Photoshop gets pretty strict about the edges. Using a big brush to fill in the large areas is fine, but then reduce the size of your brush to finish off the edges.
That's all there is to it. When it works, it's that easy.
Doing It the Hard Way
When it doesn't work, you end up with extremely unrealistic colour, like the blue eye you see to the left. Yikes. To avoid this sort of thing and get a more realistic look, I like to take a much more manual approach.
I love the polygonal lasso — it's awesome. I use it for most of my selection needs. For selecting a rough shape like an eye, it works very well. You can find it hiding beneath the regular lasso in the toolbar.
Use it to select both eyes and then copy and paste that selection into a new layer. Now we've got the original eye colour in its own layer. Desaturate the layer (Mac: Command+Shift+U / Windows: Control+Shift+U), and, if you want, auto tone it (Mac: Command+Shift+L / Windows: Command+Shift+L) to brighten things up a bit (we'll be more precise later).
Make a new (empty) layer and select the eyes again (command/control + click the layer). Use the paint-can tool to fill in a mild blue, and then set the blending mode of the layer to Colour. It'll be a little intense, so reduce the opacity significantly. Anywhere between 10-20 per cent should be pretty good.
Now go back to the eye layer (not the colour layer we were just working with — the one below it) and open Curves. If you just pull the curve up a bit, you should be able to brighten things up nicely. You'll see the blue colour pop more — but realistically so — now that the dark eye isn't so dark. When you get it to a place you want it, you're all done. Just make sure you zoom out so you know the effect actually works from a distance as well.
That's it! Got any good colour-changing tips? Share 'em in the comments.