Customer wants to us 5590 for an interior application where they would like to have the sign above an interior door that could change color when lit. I was just wondering how far away would you need to be and how dark the surrounding area needs to be for
No, You can't get the same effect inside a building.
This application is unlikely to have the desired effect. Dual color film works best when in very dark scenarios and when viewed at a distance. It could work in the right room, but it is unlikely that an average indoor room will be right. I suggest to test before doing any application like this