Quoted from BrianMadden:

We have an RGB LED DMD (wow that's a lot of letters) which can be a drop-in replacement for original DMDs. (Product page is here, I assume this is the one you're talking about?) It should work in any machine that has the 14-pin DMD connector as a drop in replacement (and like any LED DMD, it only needs 12V and not the original high voltage). My "to do" list includes testing this on all the various machine types. We have this on several of our WPC machines, but it should work on SAM, White Star, SPIKE 1, etc. (Worst case we would have to adjust some timing and add a menu option. And when I say "we", I mean ecurtz as he's the one who wrote all the code for this.)
Since those original machines just did four brightness levels of orange/red (well, some were 16, but let's just call it four for now), there's a menu where you can set what four RGB colors you want for each of the four shades. This means that it essentially can become any "color" replacement DMD you want.. set it to four shades of green or pink or orange or whatever you want. The menu interface lets you map any hex color to the original shades, so you can get really trippy and mix colors which doesn't look as crazy as you'd think in some machines. (I mean like use black, red, purple, white, for example, for the original 0,1,2,3 brightness levels.)
This DMD product also has a USB port on it where you can attach to it via any host computer and send DMD frames via the FAST Serial Protocol. In that case you get the full RGB 16.7M color options for full color DMD at up to about 20fps. That is how people use it in the homebrew community for a full color DMD.
If you are working on a 2.0 game and you want to keep the DMD look, then you could also use this DMD. It would be 4 shades (though set to any color you want) for the 1.0 / original game running via our FAST emulation (also thanks to ecurtz), and then full color for the 2.0 game.
Getting back to your actual question, at this time if you buy this RGB LED DMD and drop it into an original machine with no other FAST hardware, you will just get the ability to recolor the four original shades. It won't let you fully colorize every original frame or replace original frames.
Also quick note that the version of this DMD listed on our docs site has a lot of other components on it to allow plugging in additional expansion modules. We've since evolved our approach to this (culminating with the FAST Retro Platform we announced at TPF last month) which moves those components from the DMD to the FAST Retro Controller, so future LED DMDs from FAST will look different on the back but will essentially be functionally identical.
All that said, this space is changing and evolving quickly, and we have lots of plans and partnerships in the works. We'll keep you posted!