In this procedure for removing red eye in humans, the information in the blue channel of an image is copied over the information in the red channel. Follow these steps:
Open the image to be corrected in Photoshop. Make sure it is set as RGB (Image>Mode> RGB).
If necessary, zoom into the photo until your subject's eyes fill the screen.
Using the Elliptical Marquee Tool, click and drag to select all of the area of one of the eyes containing red.
Hold down the Shift key, and select the red area of the other eye. If you are working with a group shot, you may repeat this step as many times as necessary.
Go to the Select menu, choose Feather and set the feather radius to 2.
Click OK.
Go to the Channels palette (Window>Show Channels) and select the blue channel.
Select Copy (Edit>Copy).
Select the red channel.
Select Paste (Edit>Paste).
Reset channels to RGB and your red eye will be gone.
Deselect (Select>Deselect) and save corrected image.
The elliptical marquee tool. If not visible in this box, click and hold. Then select it from the popup window.
The Channels Palette.
To select a layer, click it. When you click the RGB channel, all channels will be selected.
Zoom into the eyes using the magnifying tool. Tip: Try clicking and dragging diagonally across the eyes for a quick zoom that'll keep the eyes centered on the screen.
