The most exciting way of getting instant color was by a process called Finlaycolor, in which, in effect, three color-separation negatives were taken simultaneously by using a grid ruled with microscopic red, green and violet lines. One then made a positive, a lantern slide from this negative, and brought it into exact alignment with the grid. This was tricky, delicate, but when one had them in perfect register, the previously black-and-white slide would burst into full color.