Also, be very careful that you aren't breaking the color pie. I have colorless creatures in my set, as well as creatures that are colored, but can be cast with entirely off-color mana (thanks to the twobrid). Designing them was like walking a tightrope. The first version of Messenger to Wilfurn, where playing it with white mana gives it deathtouch is something I'd try to avoid. The version with lifelink is much more in-line with the pie. But then, designing a cycle based around one color, and not snapping the color pie in half doing so is setting yourself up for a lot of repetition in mechanics.
And I'll echo Maledict that the M15 Clear frame seems like an odd choice for those. I'd be tempted, were it my set, to have an appropriately colored frame, but the trim would be white (which you can do with the M15 Extra template). A custom frame of sorts would probably be ideal, but they don't grow on trees.