Pretty sure eclipse pops up compilation errors when you tell it to compile and it doesn't.
You could cut out eclipse and invoke the compiler directly on your code:
$ javac ColorFinder.java
$ java ColorFinder
Enter a sentence.
Additive primary color found.
The red marks in eclipse are quite possibly the compilation errors though. And those would be doing exactly what you're asking for, spotting the locations of the errors, describing them as well.
There are also a bunch of websites where you can paste your code and get the compilers messages (including the codecademy exercises, but googling for others is about as easy)