That is great news, I was just about to order the Blair sets.
I've been working on my own graffiti as well, tracing out a variety of sources and cleaning them up for printing on white decal paper. Some of the brush style solvent based waterproof markers look promising to color them up. Some will be cleaned up scans to blend with the same markers.
I also found (but did not buy) while visiting a store here that Busch has graffiti decals. They have two sets, with HO, TT and N combined on the sheet. The quality looks good, and the HO decals would be suitable for bridges and buildings, while many of the TT would be OK on N trains.