I don't know if this is been tried before but here's something I fell across trying to find a blues tone. Most of the different amp settings tends to over do it sometimes and just can't seem to get close to what I was after. Select the metal green channel and turn the drive all the way down. Turn the channel volume all the way up. The bass & treble controls can be set to your like including a bit of reverb. The middle control is totally diiferent here on this channel as it acts more like a voicing control then just moving the mids. You'll find the more you rotate the knob to the right the more bassier the amp gets. Turning it to the left the more treblely it gets. Fiddle with this control till you find your sweet spot. You'll find this setup more warmer then the other channels with just a hint of dirt depending on the guitar & pickups being used. You might have to just slight nudge the drive control if the dirt isn't present. But make sure you keep it down as low as possible This to me seems more like using a Class A style amp just to the point of clipping. Try it and see if it works for you.

                                                                                BluesBrother