I found instructions for bleeding the Avid brake system here:
http://www.sram.com/_media/techdocs/95-5015-019-000.pdf
The instructions refer to "Avid Hi-Performance DOT Fluid" which is probably DOT 3, DOT 4 or DOT 5. In general, the higher the DOT number, the higher the boiling point.
DOT 3-4-5 brake fluids are hygroscopic and readily absorb water which lowers the boiling point
and turns the brake fluid dark. IMO, brake fluid should be changed at least yearly and anytime it turns noticeably darker.
Note that DOT 3-4-5 brake fluids are excellent paint removers!