Colored jewels?

if u crush all of the boxes in the level:)

You can get the coloured jewels by completing the bonus area of each level. You can tell which levels have the bonus levels by the plaques in behind each warp area. The non-bonus levels only have 3 slots (One for the standard crystal, one for the box completion crystal, one for the time bonus), bonus levels have an additional slot.

When you have completed the other three crystals, the "bonus" area will open on the level. You can see where this area is prior to it being open where there is a greenish outline of where a moving platform should be.

Oh, and you don't need the relic either.

To get the gem in Tsunami, you can't get the switch at the end where you blow up the nitro boxes or else it blows up the boxes to get across to the gem!!!

How do you get to go to the gem path (It looks like it would be for the Yellow gem) in Compactor Reactor?! I cant just move to that side, because it wont let me through. I also cant seem to get the extra gem in the Banzai Bonsai level, although I do get to the gem path withouot dieing..

Compactor reactor, I remember green Gem, not yellow (but I might be wrong). Once it shows up (I mean, you have it), jump on it and go.
For Bonzai, you need the Red Gem. You can die as long as you have the Red Gem.

Well, to get the colored gems you have to:
1. Not die at all in certain levels, because there's the death route, which is the only way to get the colored gems (the death routes are located in levels: 1,4,11,21,and 22.)
2. You have to... complete the death route, of course! What? I mean, did you expect to just hop on the death route pad, take a few steps and there it is? No! You gotta dodge all them doohickeys and what-nots! (The gem levels are:5*,8,12,17,and 21.) *:the level 5 death route does not follow the rules that apply to all other death routes. It's actually that little track off to the side that you could never get into. Get the level 22 gem, and it will open. Then, follow the track 'til it ends, but be careful of the nitros!