to test EI for color negatives

i am so happy i now can home test speeds of b&w negatives.  i adapted
the method from Adams's books which told me how to find 0.1 density
point on the negative by using a lightbox and a spot meter. it's
great.

now i am considering color negatives and is trying do the similar
things on them.  i always send color negatives out to a lab for
developing, and again, i dont have a densitormeter.  can i test speeds
( up to the same lab i used ) of color negatives at home?

thanks.

-
woody