I don't know of anything ready-made, but it would be pretty easy to turn a plain text file into HTML using JavaScript, with whatever content-based styling you want. You can do everything in a single client-side js/html file, so it would be very portable. It would also be very easy to add interactive filtering, navigation ('jump to next error' links), statistics, etc.
Perhaps use Markdown?
I love me some markdown, but I don't know of an implementation that includes any kind of color coding. You could of course apply a custom stylesheet that assigns colors to different emphasis tags, but then you wouldn't be able to use them for emphasis as well, if that were desirable.