You can change the colors using the tableBodyFont and tableEdgeFont attributes of the seatingChart token. I would advise using the Token Builder dialog, because it's a lot easier and those attributes are somewhat complicated. For example:
<seatingChart tableEdgeFont='{"Name":"Segoe UI","Size":18,"Bold":false,"Italic":false,"Color":"#fff","BGColor":"#048","Underline":false,"Grad":{"ColorFrom":"#048","ColorTo":"#000","Type":0}}' tableBodyFont='{"Name":"Segoe UI","Size":18,"Bold":false,"Italic":false,"Color":"white","BGColor":"#080","Underline":false,"Grad":{"ColorFrom":"#080","ColorTo":"#000","Type":0}}'>
To use the Token Builder, just use the mouse to highlight part of the text and the "Edit Token" button should become green. Click Edit Token and it will open the Token Builder dialog to easily edit the token. When you're done changing options, press OK and the proper text will be re-inserted back into the cell contents.
FYI, the reason the cell font/colors don't extend to the seating chart is because the seating chart is built using HTML tables, and IE (and other browsers a long time ago) had a bug which didn't allow the table to inherit font characteristics. So the attributes had to be added to the <seatingChart> token.