Image color overlay plugin?

Allright this might be wishful thinking, but I recently saw a page where the author had a color overlay on all the uploaded images in his posts. It looked smashing!

I was wondering if there’s a plugin I can get somewhere that does the trick for me…I rather not down- and upload all posted images again on my blog after I put them through the Photoshop paintwash..

Please let me know if this is possible and if not: WHY NOT?!
??

Cheers!
btw: would love some feedback on my site’s theme (Lush)adjustment (originally created by Marco and ported to WP by Jeriko)…check out Cargawar.com