What you would be looking to do is connect your Sirius power to you trucks ACC/Ignition wire on the radio harness.
The 12v/battery(green/purple) is the always on, this will supply constant power to your radio, this is what keeps your memory stored when you turn off the engine. You will not be using this.
The ACC/Ignition(pink/black or lt. green/yellow) is what turns your radio on, when you turn your key to either the accessory or to the run position this is supplied with 12v.
For what you are trying to do, which is have the Sirius unit turn on and off with the truck you will need to use the (pink/black or lt. green/yellow)
Also make sure you have a good ground, I recommend grounding to the radio itself and not the harness.
For the connection to the wire you will want to splice it in, I recommend against using t-taps or any other type of quick connect, they prove unreliable over time. What I recommend is taking a razor blade and carefully shaving about 1/2 inch of insulation from the ACC wire, careful because the wire is thin(but not easily cut by a razorblade). Next from the wire for the Sirius strip about 3/4 inch of insulation off. Wrap this around the exposed portion of wire from the factory harness. Wrap in about 1 inch of electrical tape. Also make sure that you add some around the insulated portions of the ACC wire and the Sirius wire to keep them together, this will act as a strain relief. Throw a zip tie over the point where you wrapped the wire together.
Normally I would solder, but I left that out of this tutorial.
And as a final note, if you end up blowing a fuse, its not going to be the one for the radio its the ACC/Radio/IGN or something along those lines.
+ Radio 12v lt. green/purple
- Radio Ground black and black/lt. green
+ (Radio Ignition pink/black or lt. green/yellow)