If you want a default edit, it can't be posted on the forum due to copyright reasons.
With that said, it's easy enough to make yourself. With a few Google searches, you can probably figure out how to set it up as a batch command in GIMP (which is freeware) to make all of the default textures monochrome. I'll direct you to the All-Inclusive Guide to Texturing to help you get started in getting the default textures to alter. Beyond that it's up to you.
Keep in mind, though, that there will still be some colored things. Text and sky colors are hard-coded. As are fog colors and a lot of other things. You're going to have to use some advanced Optifine features if you want a complete monochrome pack, which might take some doing.