Pull a brown paper bag over their heads? A wig and dark glass? 'tufa surgeon? Sorry, lol!

I'm assuming since their black that you used a dye. Mix up a batch of 'tufa with little or no black (charcoal)dye, place your cow pies on a piece of plastic sheet and cover them with a layer of your new mix. Let them setup and use a piece of real rock to texture or carve your rock to give it some detail. You can use arylic paint to "flick on" and "smudge in" a little color.
I've also taken some of my cow flops, wrapped them in pretty packages and left them on friends doorsteps. Unfortunately, some do find their way back here cause most friends know who does the great wrapping. Aren't you glad you don't live around here! lol Billie

Thanks for giving me several ideas
They have begun to dry some and look less dark
I did not use dye. If I can work on (apply more tufa') perhaps I can make them more acceptable.

Thanks
Martha

If you used no dye why were they black. Portland gives you a grey look not black. What recipe did you use?

I had just unwrapped them from the plastic they were in. They are now more like cement. But still not pretty.