I'm going to guess that this is not about color seps, but about separator rules in tables.
I'd start at:
Click in table.
Table > Table Designer > Ruling > Heading and Footing Ruling > Separators:
You might need to also use:
Table > Custom Ruling and Shading [Show Current Settings]
to discover just what is "out of range", and at this point I'm out of guesses.
Stroke weight greater than page height might do the trick