In Turok 2, the Charge Dart Rifle has different strengths to 
its shots depeding on how long you hold the Z button. Also, 
the longer you hold the button, the straighter and farther 
the shots will go. Here is how long you have to hold the Z 
button to attain the different levels... 

Red - Shocks the enemy for approx. 5 seconds. Tap the Z button. 

Orange - Shocks the enemy for approx. 10 seconds. Hold the 
Z button for about half a second. 

Yellow - Shocks the enemy for approx. 15 seconds. Hold the 
Z button for about a second before releasing. 

Green - Shocks the ememy for approx. 20 seconds. Hold the 
Z button for 2 seconds. 

Blue - Shocks the enemy for approx 25 seconds. Hold the 
Z button for about 3 seconds to attain this shot. *NOTE* 
This takes 2 away from your ammo instead of the usual 1. 

Purple - Extremely straight shot that shocks the enemy 
for 30 seconds. Hold Z for more than 5 seconds to get 
the gun to shoot this. *NOTE* This takes 3 away from you 
ammo instead of the usual 1.