self.__chips now contains the list of rgbtuple values for the
chips named i - 1 (Tkinter counts from 1, we count from zero).
The chip number was just the index + 1. This means color lookup
need not do an itemcget(), it can just index into __chips.
instead of calling __canvas.itemconfigure(), we glom up a huge Tcl
script and call tk.eval() directly. Actually we do many appends
to a Python list, then string.join() them together into one huge
string. This reduces the overhead of Tkinter but making one fast
call to Tcl.
Barry Warsaw