Can someone explain them to me?  

I've only noticed color in them. The power of Crayola!  

5 consecutive kills-blue-speed boost 10 secs
full health-light blue-idk
50 consecutive kills-yellow-idk

that's all I know  

Posted by Ace

5 consecutive kills-blue-speed boost 10 secs
full health-light blue-idk
50 consecutive kills-yellow-idk

that's all I know

Light blue gives you more hp while healing...  

I didn't get any pk reward at five kills...  

Posted by Lazerlatté

I didn't get any pk reward at five kills...

like kills that happen really near each other.
1 kill(0.3 seconds) 2 kill (0.45 second) and so on.  

personally i think the pk reward system is just dumb.
the pk reward system should be for spar and the spar reward hats should be for PK.  

Posted by Ace

5 consecutive kills-blue-speed boost 10 secs
full health-light blue-idk
50 consecutive kills-yellow-idk

that's all I know

That's what that thing was, I got one of those and didn't realize it was a pk reward. I thought it'd be a tangible item.  

Posted by Mr.$imons

That's what that thing was, I got one of those and didn't realize it was a pk reward. I thought it'd be a tangible item.

I did too, at one point. Btw for some reason I randomly got a pk reward while I was healing in the hospital after being killed, it wasn't immediate but after like by the time I was fully healed. It was the one that boosts healing.  

what does green and gold do?  

Posted by fsh

what does green and gold do?

I'm uncertain, but I suppose Green is more damage, and yellow, uh maybe it does all of the above? Hehe// it's for 50 streak