The blue gun is incredibly fast to get, it however does require some unconventional puzzling.
I can't say much more about getting the blue gun without spoiling some of the fun of doing so. So here's a map of where to go to get it.



Map not good enough? Watch the video to spoil it proper.

The Green gun is pretty easy to get. Only 1 space bending puzzle and a lot of sequencing.
All you have to do is proceed from where you got the blue gun, collecting and keeping all the blocks along the way so you'll have enough for the 4 block door. After that all that's left is a space bending puzzle that I'll spoil after the map.
So the trick to this last puzzle is to not look away from the door. If you look away the door will disappear and you'll have to start back at the 3 block doors, or even as far back as the blue gun.

The yellow gun is a lot more fun to get than the green gun, and requires you use some hidden features of the green gun. Steam kinda already spoiled those hidden features in Antichamber's description when it mentioned the existence of guns that can "create, and destroy matter". The green gun is the first gun that can do this. I'll spoil how to do that in the video, but here is the map so you can try these puzzles on your own first.
Need the extra direction? Here's the video for it.

The red gun is pretty easy to get. Seriously, there are only 2 short puzzles to get in your way. It's also the best gun for generating blocks. Here's the map of it's location.
And as always the video of how to get it.

Though the map for the end game is short you do a bit more running around than it would suggest. I'll spoil the details of how you get the black gun and finish the game in the video.

Map not enough to help you escape? Try the video.

If you've made it to the end of the game then you've already encountered all the tricks of this game that you'll need to uncover the rest of the map. This map here won't help you much with any of that, but here it is anyways.
Enjoy exploring the remaining nooks and crannies and finding all the hidden goodies this game has.