Here is an article that can help you change every icon on your computer, without the use of programs. Note: If you don't use the free LiteIcon program, you won't be able to change the Finder and Trash icons.
Steps
Method 1 of 2: How to Change Application Icons
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Step 1. Find the icon of the application to change (for example Safari)
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Step 2. If the application is in the dock, right click on it and select Options, then Show in Finder
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Step 3. If the application is not on the dock or desktop, right click on the folder and select "Get Info"
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Step 4. Once the information window is open make sure your permissions at the bottom of the page are all set to read and write
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Step 5. Click on the icon image in the upper left corner
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Step 6. Find the icon to replace the old one with and copy it
(You can find some beautiful icons here)
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Step 7. Make sure the icon in the left corner still has a blue frame
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Step 8. Go to Edit and click Paste, and the icon should change
Note: If the icon has not changed, log out and then log in again to view the changes.
Method 2 of 2: How to Change Finder and Trash Icons
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Step 1. Download LiteIcon here
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Step 2. Open LiteIcon
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Step 3. Click on the 'Dock' tab
'
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Step 4. Find the icon to replace the finder or trash icon with
Note: You will need to indicate two icons for the recycle bin, empty and full.
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Step 5. Drag the new icons to the boxes where you see the original ones
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