Only if you use an alternative launcher such as Apex or Nova. With sense you cannotI wish it were possible as well...I don't know why manufacturers don't like at least giving us more customization options when it comes to things like that. I mean it's not going to do anything but make more users satisfied..
I'm pretty sure the buttons are always lit when the phone is, they're just very subtle so that you can see them when it's dark, but when it's light, you can barely tell that they're on (which I think is pretty cool since they're etched in white anyway).