MX Blue: Tactile, with a moderately loud click at the activation point, which is pretty near bottoming out. Great for typing, and great for my gaming style, which is moderate to moderate-heavy MMO and strategy gaming, although the style of activation point may not be ideal for FPS gamers. They require 50 grams, or 60g max, to actuate, which is relatively light, but not so light that you accidentally press one by resting your hands on them.
MX Green: Almost like Blues, but with MX Black springs; they are near identical to the MX Blues, but require more force to activate - 80cN, to be exact, which is 30 grams more to actuate than the Blues. Great for typing, if you prefer the "resistance" of the Blacks, but otherwise, Blues may be a better option if you still want a click.
MX Brown: Quiet, tactile, and relatively light, with no clickly feedback, but a tactile bump instead, that signifies the actuation point is directly below, and will be hit. It has noticeably less feedback than the Blues, Clears, or Greens, but is still an enjoyable bump; very gratifying, but not nearly as much as Blues, in my opinion. They require 45 grams of force to actuate, which is relatively low, but still not "dangerously" low. Very easy, and enjoyable to type on.
MX Reds: Reds are, in every sense, lighter versions of the MX Blacks. They require only 45 grams of force to actuate, and are a linear-style switch, like the Blacks, meaning there is no tactile bump or click; instead, you bottom out the keys to guarantee they actuate, similar to membrane switches, but much more "solid" and long-lasting.
MX Black: The base of the Red, and ghetto-Greens, the MX Black is a linear switch, that requires some of the most force out of all MX switches to actuate, save the Greens. It's the basis of the Reds, so everything I've said about them still applies.
MX Clears: Also a tactile switch, like the Brown, but requiring more force to actuate. I, for one, enjoy a "resistant" keyboard, like Topre switches, at least, or MX Blacks. The Clears require 55 grams of force to actuate, which is slightly above "average", but not noticeably. The tactile bump is also enjoyable, as with the Browns, but Clears come in much lower supply, so if you can't find them, Browns are probably the best replacement.