I second 223spree's recommendations:
My department uses WinQ3131A (made by IMI) for all our quals and training with great success. The ammunition is low flash, clean, accurate and consistent.
I recently shot almost 2k rounds of PMP at a Pat Rogers course at Gunsite. Note the PMP comes out about 200fps slower than most M193, but it is very consistent as well. Out of my stock Bushmaster barrel, non-free-floated with gadgets hanging off it, I managed a 5rd group just under 2.5" at 200 yards. It also had remarkably low flash.
PMP ammo is Praetorian Metal Pressings, a division of the Denel Group, which manufactures ammunition for the South African military.
I get all my training ammunition from John Koppel at ProLoad. He's a stand up guy with competitive prices.www.proload.com
PS. 5.56mm will run fine in your Colt.