Yes, there are additional color schemes and themes for NetBeans and they can be downloaded through the Plugins page created by the developers. The themes are also developed by other NetBeans users. Access the Plugins page below.
Plugins page: http://plugins.netbeans.org/PluginPortal/
Once you download a theme, open NetBeans then go to Tools > Options > Import and select the ZIP file you've downloaded.
Tip: To narrow down results to display only themes, use Fun Stuff option from the Category drop down menu.