eclipse jsp - no colors, code completion and error detection

Are the JSP pages opened with the right editor? Right click on your JSP file -> Open With -> JSP Editor. You can set the editor in Preferences -> General -> Editors -> File Associations.

Is your project declared as a "Web" or "J2EE" project? If not go into the project facets and add the "Dynamic Web Module" facet to it.

At that point your project /should/ be recognized as a web project and the highlighting and syntax decorations will be enabled.