Tartrazine washes out of the Matrix during processing. I don't know what the final yellow imaging dye was, but the conditions are different for dye the dye imbibition step and the transfer step so I don't think there would be a problem using tartrazine for two purposes.

You might want to check Jim Browning's work, as it may indicate problems with other receiving sheets without Thorium salts. A salt is needed for proper image stability. The dye must remain in the proper "matrix" for proper stability.

PE