I got the yellow ones on my bolt for my '05 black magic, and I think I've got orange ones on my valve to my old "small valve" cocker (mine's a 1998 PTP, however your 1997 sniper might use the same o-rings). The blue ones might be for a ram, not sure though, typically you don't open those up. And lastly- the screw does look like a valve lug to me.
'07 Angel G7 Joy Division
'05 Dye DMC /w X94 bolt
'05 WGP Black Magic /w MQ2
'03 Dye Matrix /w X93 bolt
'01 Shocker Sport Turbo /w old school Maxflo 4500