Manually Change the Color of Your Dock in Mac Os X Leopard

Are you a little sick of the default grey Dock? Look no further...

Steps

Go to Macintosh HD > System > Library > CoreServices > Dock.
Right click, and click on Show Package Contents.
Go to Contents > Resources.
Find the four S curve files and drag them to your desktop.
Make a folder for them called 'Default'.
Copy and Paste the folder, and rename it to 'Modified'.
Open the first file in your 'Modified' folder in Preview. Go to Tools > Adjust Color.
Drag the sliders around until you like the color. Remember the positions of all of the sliders (taking a screenshot may help).
Save the file.
Modify the other three files in the same way.
Copy and paste your 'Modified' folder and rename it 'Files to Use'
Go back to the Dock's Resources folder in Finder. Delete the original Scurve files by dragging them to the Trash (this will require an Administrator password).
Drag the files from your 'Files to Use' folder into the Resources folder (this will require an Administrator password)
Delete your now-empty 'Files to Use' folder.
Close all of your Finder windows and Restart your computer.

Make sure that your Dock's position is set to horizontal, as the vertical position will not show up your colored Dock.
If you are trying out lots of different colors and don't want to restart all the time, try opening Terminal, then clicking Shell > New Command and then write 'killall Dock' (without the quotations) to relaunch the Dock.
There are lots of replacement Dock designs available on the Internet, so have a look around if you are after something more dramatic.
There are quite a few applications available that do this process automatically, so have a look at them if you want a quick Dock change.
You can try this process on the Trash can picture, or any other pictures on any application if you want a color change.

Make sure you save the default files, you never know when you will want or need the default style back.