More like black when they coincide - those are filters, one of which blocks everything but blue, one of which blocks everything but red. When the co incide you won't get much blue and red (purple), because between them they block everything (this kind of filter isn't perfect, which is why you do actually get a slight purplish tint to your black as a little bit of red makes it past the blue filter and visa versa).
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Date: 2009-06-13 02:07 pm (UTC)no subject
Date: 2009-06-14 08:31 am (UTC)