Iconography experts:
Identification of True/False, Yes/No, Affirmative/Negative is a normal requirement... everywhere. In North America, common indicators for these are Red/Green or check/X symbols
There are known problems with these indicators: red/green is a common form of color blindness, and (most scarily) the symbols have the exact opposite meaning in different regions.
Is there a set of symbols that may be less well known, but still easily recognized, and more consistently understood internationally?
UPDATE: A green plus fails... it conflicts with ISO First Aid Symbol (yarrg!!)