I am actually using Post-it Arrow Flags. The original package comes in the four colors previously mentioned. Turns out 3M makes two other 5-packs. One is the "bright" collection in highlighter-type colors, while the other one just adds purple.
Blue can be used for water.
More options are always better. The problem is merchandising. Apparently, Office Max puts these items at the opposite ends of the Post-it section. I suggested they moved the together.
Your changes will be made by EOD Pacific Time.
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