how challeging are the blue and green trails? like are there any drops if so how big? and how much suspension travel would you need to ride the blue and the green or even the black (no double black)
Everything in whistler below the black diamond level is easily ridden on a short travel bike or hardtail, most of the black diamond trails are also ridable on a short travel bike or hardtail, but they a lot more skill and confidence to go the proper speed on a smaller bike. EDIT: Actually everything in whistler is ridable on a short travel bike, most people just would rather ride a bike more appropriate to the terrain.
Everything in whistler below the black diamond level is easily ridden on a short travel bike or hardtail, most of the black diamond trails are also ridable on a short travel bike or hardtail, but they a lot more skill and confidence to go the proper speed on a smaller bike.
Do not ride the black diamond trails on a hardtail, if you are at all worries about your ability to ride the blues and greens. Sure they are rideable, but they are not the place to take it easy and stop to scope out lines. Riders come through fast and furious, with huge consequences for both if someone is scoping the lip or a technical line unaware of riders coming.
If you really want to scope something out here's a tip. Leave your bikes well off the trail - in the bushes, just because it doesn't look like a line to you doesn't mean that it isn't. Have one guy stand look out up the trail to give warning when riders are approaching, and know where you are going to get out of the way to when someone does come down the trail.