I need to have a table cell in HTML which is transparent, but not 100% transparent... a slightly red- or- blue-ish tinge on what shows through.

For example, on this site
http://www.guardian.co.uk/
note the gray vertical bar on the right. As you click the headings on that bar, a semi-transparent window pops out.

I don't need the popups, but I need the semi-transparent tint coloring. Any ideas how to do that?

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