只对5以上的版本有效，官方网站上有的，不过很多人没看到罢了
Spicing Up Your NetBeans IDE 5.0 With Substance
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This tech tip shows you how you can spice up your NetBeans IDE 5.0's look and feel with color themes, custom button-shapes and watermarks (wallpapers) using Kirill's Substance plug-in. To use Substance with IDE 4.1 or any other Swing-based application, refer to Spicing Up Your Swing GUI With Substance.
Getting to Know Different Themes
Creating Your Own Look and Feel
Preparations
The Substance Look and Feel NBM works with JDK 5.0+ in NetBeans IDE 5.0 (development version).
If you want to integrate a watermark into your Swing application, you need a suitable (wide) wallpaper image file. Download this aquamarine JPG from digitalblasphemy as a sample.
For some features, you need to know how to access your operating system's commandline
To install the substance-netbeans plugin into NetBeans IDE 5.0,
download substance-netbeans.nbm from Kirill's project page and save the NBM file to your home directory. For this tutorial, I am using version 2.1_02.
To plug the module in, open NetBeans IDE, and choose Tools > Update Center from the menu. In the Update Wizard window, check the box next to Install Manually Downloaded Modules (.nbm files), and then click the Next button.
In the next screen, click the Add Button and select the substance-netbeans NBM file you just downloaded, then click OK. The NBM file shows up in the list of modules to install. Click the Next button.
Make sure the NBM is visible in the field labelled Include to Install, then click the Next button. If a license agreement comes up, click Accept and then Next to proceed.
A screen with the download progress bar appears. Again click the Next button.
Check the Include box next to the line saying "NetBeans-Substance". If you are asked whether you really want to install an unsigned module, click Yes to proceed.
Click the Finish button. If you are told that the IDE must be restarted, check the box saying Restart the IDE and then click the OK button.
After the IDE has restarted, look into the View menu: If you see four new menu items, Button Shapes, Colors, Themes, and Watermarks, the plugin was installed successfully.
http://www.netbeans.org/kb/50/substance-look-and-feel.html#creating
按着步骤作就行了，先要下载一个.nbm的插件。写的挺简单的一看就能看懂了。