Can FolkArt Sign Shop Stencil Paste be intermixed to create new colors or perhaps different values of the same color?

Yes, FolkArt Sign Shop Stencil Paste will mix well within the colors of each variety set.  Simply squeeze out a small amount of each color to be mixed. Begin by adding a small amount of the darker color into the lighter color, then continue adding small amounts of the darker color, a little at a time, until the desired color or value is achieved. It is recommended to use a palette knife to mix two or more colors when creating a custom color.