What tastes like marigold?
Apparently marigold is quite common in Georgian cooking. I found the following excerpt on this  page :


  Marigold is the "saffron" of Georgia, and although only a little is used, it does make a difference to the colour and flavour. Now, you might think it might be hard to get the spice marigold in Japan, but you would be wrong! I know of at least 3 sources (1) super-premium organic marigold, (2) reasonably priced marigold tea, and (3) super-cheap marigold petals from my favourite spice shop, Ohtsuya (I am sure I saw the powdered spice in their shop, as well). 


Most references I found say that marigold has a citrus flavor as noted below from this  link :


  Marigold (Tagetes tenuifolia - aka T. signata) - The marigold can be used as a substitute for saffron. Also great in salads as they have a citrus flavor.


Also, in looking at recipes for Georgian Satsivi I found several that called for saffron rather than marigold. Personally I would try saffron as I think it would work well with the flavor profile of the sauce.