Use Red, Green or Blue Channel
Elements does not have a Channels Palette and therefore you can't
select just one color channel... or so it would seem. Fortunately Adobe
have provided Elements with the facility to select individual channels. While
this is not as powerful as the Channels Palette in Photoshop 6, it does allow
you to perform most of these operations.
Each of the Red, Green or Blue Channels can be selected and then operated
on independently of the others. This means that you could blur just
the green channel, leaving the red and blue channels untouched. Or
copy just the Red Channel and paste to a new layer.
When you select one of the channels, the on screen image will be shown in
monochrome representing the selected channel. The title of the image
will change from '(layer name, RGB)' to '(layer name, channel)', for example
'(background, Red)'.
When you have finished, selecting the RGB Channel will return to normal.