There is a repeatable ‘Hunting Contract’ mission for each color of snake. All the missions are for 1000 kills. 
Green Snake level 17 Copy WP to Clipboard
Purple Snakelevel 18Copy WP to Clipboard
Brown Snakelevel 19Copy WP to Clipboard
Coral Snakelevel 20Copy WP to Clipboard
Black Snakelevel unknown a few rumors, probably need to ask a local or post the question here
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