If you enjoy using the Color Splash iPhone app, you might also want to try TouchOfColor. There's a free version if you just want to try out the app. The full version only costs 99 cents which I think is worth it.
Anyway, TouchOfColor is easier to use compared to Color Splash. All you need to do is to select any color from your chosen photo using the dropper tool of the app. The color chosen will automatically stand out while the rest of the image is turned to black and white [or select the background color to sepia, solid black, solid white, solid gray, red, green or blue ~~~ you can set this in the "settings" section of the app]. You can adjust the strength of the color to get the result that you want. You can choose two or more colors that you want to stand out in your photo ~~~ great!
Try it and enjoy!