So now we can hear from those that hate tab colors.
Yeah, that would be me. A couple of my finance colleagues colour tabs - probably in the spirit that you describe, except that I don't know what the colours signify. And they're not even nice pastel colours!
...colour every single cell with data based on the type of data in it and/or the value.
i'm waiting until you can put pictures on the tabs - perhaps even small thumbnails of the sheets.
That might save the user actually looking at the worksheets.