Looking for help with headstone form

I have a bronze(?) military headplate for my husband's gravesite. I want to make a tye - dye effect concrete or acrylic(?) form to put it on. Does anyone know about a product called whitecrete? Is it very expensive? How about the acrylic/poly resin? He was not a dull person and I want his headstone to reflex him not just some dull concrete slab with the plate attached to it. My idea is to make the form about 6" wider than the plate on each side, make batches of the whitecrete in the colors he would like, pour them into the mold which would have dividers in it until all the colors were poured. Then remove the dividers and use a stick to swirl the colors into a very loose pattern. Does this make sense to anyone else? I would like to use very vivid bright colors. I read a couple threads about where to get the colors, now I need to find the whitecrete or acrylic and draw advice from those experienced in working with whitecrete/colored concrete/ poly resin. Any help will be greatly appeciated. I am walking into something I know little if anything about.