The presently claimed invention relates generally to color signal processing. One claim recites a method including: obtaining a measure or value associated with one or more color characteristics of data representing video or imagery; based at least in part on the measure or value, determining for the data those samples that should receiving steganographic encoding; transforming at least some of the data into a transform domain; and utilizing a programmed electronic processor, altering transform domain coefficients of the at least some data that has been transformed to steganographically encode the data. Of course, other claims and combinations are provided.