[jstimpfle]

It's very easy to get wrong. Often, the syntax categorization itself is wrong because of parser issues (it's hard to get right in C IDEs. Java should be fine here).

Then, it's a question of what should be emphasized. Many syntax highlighters emphasize syntactic structure too much, making it hard for the programmer to concentrate on the content. I use Visual Studio for example, which is relatively unobtrusive (pastel colors) compared to e.g. the typical VIM color schemes. Visual Studio will color macro names, function names, variable names all in different colors - roughly purple, bronze, black. I just noticed it even colors function argument variables different from global variables/functions and member names. I don't think that's helpful for reading code. It's a distraction.

[mst]

I certainly often find it distracting - it's notable that e.g. elvis' default highlighting, which mostly just slightly bolds {} and () and similar, doesn't bother me at all, though I get most of the same advantage out of 'showmatch' in vi.

(see my sibling comment for the fully verbose version)