A good VHDL editor is terribly important during all the phases of your design cycle.
Both Altera Quartus and Modelsim simulator include their own VHDL editors. Both tools include syntax highlighting. In the case of Altera Quartus editor, there is a very useful feature which is the possibility of entering templates for commonly used code blocks (entity, architecture, component) and also for design units (counters, registers, memories, etc.).