The file item icon and the folder icon is more than just a cute image in the Kawa project tree.
As shown in the figure above if the file item is red in color it indicates that the file is dirty and it needs compiling. Conversely, if the file item is green it indicates that the file is clean. Similarly, if a closed sub-folder has a check mark sign as shown in the figure above it indicates that the sub-folder has all clean files under it and if the folder has a cross mark it indicates that the sub-folder has some dirty files under it.
These indicators are updated when a file is saved or compiled, after Build/Rebuild All command, Build/Compile *.java command, Rebuild Folder command and Compile *.java folder command. It is possible for the indicators to not indicate correctly some times. Selecting Updates Images from the Project item right button menu in the project tree will update all the images.