Is it possible to read the parameter of an effect?

I'm trying to change the colour of an object using the HSL effect every few seconds, and I'd love to be able to make the background colour a complementary colour.

Is it possible to read a parameter in the HSL effect to do this?

For example:

Every tick set background HSL parameter 0 to object HSL parameter 0 - 50

Cheers

EDIT: Kind of figured out how to do the basic effect I was after, but still keen to know if those values can be read.

If there's a way to do that I haven't heard of it, but if you set the values you need to see to variables you can just compare the variables instead.

Yeah that's what I figured. Thanks!