meeotch wrote:Are the pieces that are designed to couple 2 axles together different colors for different sizes to aid in not puting the wrong angled piece on while building?
This doesn't answer your question, but...
I'm assuming you're talking about pieces like this
Here's a fun fact that I recently discovered: each of these types of elements has a number on them that corresponds to their given angle:
1 - 0 degrees
2 - 180 degrees (PI radians)
3 - 157.5 degrees( 7/8 PI radians)
4 - 135 degrees (3/4 PI radians)
5 - 112.5 degrees (5/8 PI radians)
6 - 90 degrees (1/2 PI radians)
You can use these numbers to determine which type of angle you should use.
meeotch wrote:Does the above question also explain the different colors used for the axle pins?
To determine an axles length, place it alongside a brick or plate and see how many studs it spans. For example, if it spans 4 studs, it is a 4-length axle. LEGO's method of coloring axles is actually quite simple: even-length axles are black while odd-length axles are light-grey. (Also, axles with stoppers or other weird things are usually dark grey.) The only exception to this is 2-length axles which are increasingly being made in red (I suspect this is to help differentiate them from black technic pins). This is actually a nice way to help differentiate similarily sized axles. For example, while it's fairly easy to differentiate a 4-length axle from a 6-length axle, it isn't as easy to differentiate a 4-length from a 5-length without examining them closely side by side. Making them different colors makes sense.
If you've ever wondered why some technic pins are light grey while others are black, there is a reason: black technic pins have something called "friction ridges" on them while grey ones do not. What does this mean for you as a builder? If you connect a tire using a grey pin, it will rotate freely and quickly, but if you connect it using a black pin, it won't spin nearly as easily, due to the increased friction due to, you guessed it, the "friction ridges."
The moral of the story here: LEGO likes to use different colors for pieces that look very similar but function differently. This helps us, the builders, differentiate between pieces when we're assembling the set.