Artificially yellowing white marble

I have an old victorian Marble (http://www.lightemprador.com) mantle (8 piece kit) that is white with grey
veins but yellowed somewhat presumably from natural ageing and (http://maplered.com) other
factors. My dilemna is that when I relocated the mantle to my bathroom I had to elevate it off the floor some. I had extra Marble (http://www.lightemprador.com) that was also white
with grey veins but not near as yellowed that I had cut for me to act as a
baseboard to cover up my shimming wood. Is there any way to yellow the
baseboard  Marble (http://www.lightemprador.com) pieces to more closely match the natural yellowing of the antique mantle?