Nice setup. I have the Ameriglo i-dots on mine and Ameriglo is sending me a Orange front this week. I think that color is the easiest for my eyes to pick up in all light conditions.
I first started with the Dot/post sight setup on a old W.German Sig 226. I notice all my first time shooters shot far better with that type of sight picture than the standard three dot setup. I switched to the rounded U-Notch rear on my Shield and love it for quick acquisition and follow up shots. They seem offer the best compromise between the XS Big dots and a stock three dot setup.