The Photoshop color channels can be found via the window menu and channels. If you are currently in RGB image mode, the channels panel will display the red and green and blue. If you are in CMYK then you will see the cyan, magenta etc
The panel displays the current ones but it can also be used to add additional ones. Go to the red (or cyan) and click that and you are now working only with the red pixels, the green etc are ignored. You can then apply a gradient or brush stroke just to that and also combine that with a filter. You can then go to the green and apply a gradient or effects such as the blur to that and repeat with the green. You can always return to RGB or CMYK by clicking that entry in the panel.
You can repeat this numerous times. You can simply go to the entry again and again and apply the effects and the other tools to red or green etc and then return to RGB etc
It is a pity that the thumbnails are not very big so it is hard often to see the work in the red and the green and how they relate (other applications do it slightly different and have the navigator show the full picture).
You can also do the same in other modes via the image menu so if you go from 8bit to 32bit (for even more stunning colorful designs) then you will still see red and green and blue. The only difference is that on returning to 8bit you will see the HDR panel. You can apply most effects to the red or green etc but some effects are grayed out and you will need to use the split and merge method to enable you to add effects to those (please check out that tutorial). The brush strokes and shapes (pixel mode) can also be added to the design in the red or the green or the blue.
You can also use a selection with the red or green etc. Go to the red and select the rectangular marquee tool from the tools panel and create a selection. Apply a filter to the image such as a blur and then deselect. Repeat this in the green and also in the blue but in different locations and then return to the RGB and you will see a very unusual blur (or whatever) effect applied to the different selection areas in the red, green etc