Project Builder in 10.2 exhibits a very annoying coloring scheme in the build pane (at least if you set your selection color in General Preferences to light blue). Clicking on error messages gives them a dark blue background behind their red font which makes them pretty much unreadable. But there's a fix to it. Open the Terminal and type:
% defaults write com.apple.ProjectBuilder \and then restart ProjectBuilder (the above should be a one-line command; the backslash should allow copying and pasting). There's more information on this in the Release Notes for the AppKit on Apple's Developer site.