... blue, but many colours are now available. Power Tack can leave an oily stain on paper materials if attached for a long period ... -toxic, and it won’t dry out.. Reusable adhesive.It can be used to mount Maps, Posters, Charts, Calendars, Planners, ... .CAUTION ADVISORIES OR SAFETY RECOMMENDATIONS:Power Tack may leave some oily residue on some surfaces. Do not use on soft flocked wallpaper, newly painted ...