I've done this with Ruby and set the color to light gray. My co-workers wanted to have C/Java-style parens around damn near everything (except when they didn't; the reasoning to omit them was something along the lines of, "But, see, here it's a DSL." )
They strike me as line noise and make it harder to read many things, so I lightened up the color in my vim syntax files to give the appearance of more white space.
I had mixed results. Yes, it was far more readable to me, but there were times when a paren was missing or mistakenly added, or the spacing was off (another coding standard violation), and so on.
Now that I code on my own, the new coding standards say no parens unless required by the language. I also changed my syntax coloring back to more clearly show parens.
Heated debates amongst programmers (coworkers) about marginally important questions such as indenting styles, parenthesis usage, naming conventions, source code directory structure, etc. are always very amusing to observe. I usually sit back and just watch the show.
Srsly, looking past the brackets is the least problem in reading lisp. The harder part is dealing with the lack of syntax, so you have to remember place structures instead of picking up hints from the punctuation. And in that regard, Pythonic indenting makes it harder.
Nearly every Lisp development environment does that. SLIME, the poster child of excess does this as well. I don't think I matched parenthesis, indented or looked up a documentation since 2005.