Selection Tags lookup

Hi, I have a combo and a selectionTags object on my page. The combo is linked to a DB that contains colors. When the user selects a color, it is added to the selectionTags collection. If the user picks the same color twice, I don’t want it added to the selectionTags a second time. How do I search the selectionTags collection to make sure that color is not already in there? Thanks.

Please describe your collection schema (structure. what fields/columns you have etc…).