There are a couple of ways I change my dock icons.
First I use and app called LiteIcon, which works for some. Simple app that allows for drag and drop to change icons.
Others I will change manually. This I do by using an app called iConvert iCons, which allows me to build my own icons in Photoshop or Illustrator and then convert them. Then I will find the app I want to change the dock icon in my Applications folder, right click on the app and click on Show Package Contents. That will open the Contents folder. Inside the Contents folder is the Resources folder. Inside the Resources folder you will find the icons for the dock. Just name your new icon the same as the icon inside the Resources folder and then paste it in. It will ask for you admin password and to replac the other icon. Sometimes it requires a restart or logout to make it show.
One thing I always do is keep a copy of the original icons before changing them just in case I want to change them back. Be careful inside the Package Contents. You do not want to mess anything up as it can affect how you app will run.
If you have a hard time with any, as some can be stubborn, feel free to fire back with further questions. Below is a sample of what I have changed my Firefox, Mail and Finder dock icons too.
Thanks for your reply, appreciate it. I know how to change icons and folders, just looking to change the red badges. For example the red badge over app store updates or when new mail/messages come in...make sense?
step 1) Navigate to "System/Library/CoreServices/<<right click on the Dock.app and hit show package contents>> /Contents/Resources/"
step 2) navigate to "System/Library/CoreServices/<<right click on the Dock.app and hit show package contents>> /Contents/Resources/"
step 3) Select 'statuslabel.png' and open it in preview then export it to you desktop or other location
step 4) Modify the exported statuslabel.png to a color of you liking
step 5) Go back into "System/Library/CoreServices/Dock.app/Contents/Resources/"
step 6) Select the original 'statuslabel.png' and go to File > Get Info, or push Command+i. In 'Name & Extension,' rename the file to 'statuslabel.png.backup' (Append '.backup' to the file name). You will need to enter your password to do this.
step 7) Copy and paste the modified 'statuslabel.png' into the aforementioned folder. You will need to enter your password again.
step 6) Quit the dock app via activity monitor or terminal and relaunch it (note: it should relaunch automatically if you use activity monitor i don't know about terminal though)
you have now changed your dock icon badges!
note: i would not recommend changing the shape or using a different badge icon to replace the statuslabel.png icons. As the statuslabel.png and firstname.lastname@example.org icons are designed to be just the right size and are at just the right height. i learned this the hard way when i tried using a duplicate of the modified statuslabel.png to replace the email@example.com and rendered all my badges unreadable.