Your caps are most likely the stock gibson ceramic capacitors. Throwing in some PIO's should help you get a brighter tone.
nothing personal, but there is so much horrid information in this thread starting with the above.
If you were designing a circuit, there is no construction of capacitor that will get you "bright" faster than a ceramic. This is the lesson you learn in the first ten seconds of the first day of the tuning an AC circuit 101. Ceramic caps are bright, they are bright at high impedance nodes, low impedance nodes, bright all the time.
Conversely, making a generalization, the darkest caps you can usually find are paper in oil caps, save for the exceptionally rarer mylar in oil which are the darkest caps I have ever heard personally.
Putting a paper in oil cap to brighten an AC circuit would be akin to putting a ford explorer in the water to go sailing...
Of the dark dark paper in oil caps commonly available today, those sealed metal russian mil caps without the epoxy paint on them are at the top of the list for dark and in general they are lousy choices for guitars as they all need to be formed up with high voltage before they sound anything but dead. They will heal for sure, but if you take them off the shelf and just solder them in you are not hearing that cap conducting the way it should... It can not be stressed enough that these caps need a forming voltage on them first to get the ideal performance out of them, theyve been sitting for eons and the fact that they are sealed doesnt impact this discussion. Since there is no high voltage present in a guitar, they need to be formed and if you dont, they are always gonna sound dead and if you dont think they sound dead and you havent formed them up, you're head will spin around three times if you form them and then listen...
You want a non-sectional polypro cap in there if you are going for bright. you can do that cheap with an orange drop but there are much better choices out there if you open a hifi catalog.
Now all this talk of caps is completely moot if the original poster is playing with his tone on 10, which logic would dictate he is since he's complaining about a guitar not being bright enough... On ten, those caps arent doing much. The whole point of those caps is to build a treble bleeding LC network, they are there to DULL, you've gotta look elsewhere to bright.
Far better places to look are the stop tail material first, bridge and saddles. Then the pickups next, all the 498s Ive ever listened to are very dark sounding pickups.