Totally agree with David. This style of coloring glass is very common, particularly for less expensive Murano glass. I have never seen the name of the technique. There are no lines in this type of glass, so no indication it is incalmo. Heating to fuse the glass would negate the point of the incalmo technique. I have a feeling the glass is just rolled in the coloring substance, then heated to develop the color. I've never seen it done, however, so cannot say.