In particular, Vivi's Persistence looks like it will be a welcome addition in either Vivi or Kuja commander decks
This creature is all creature types and will allow us to pay X mana to make our creatures X/X and gain all creature types until end of turn
Therefor I dropped Manamorphose from the deck
Tatyova, Benthic Druid Tatyova, Benthic Druid is a straightforward and very popular Simic commander
Still, if you don't already have the rare duals, replacing them with Contaminated Aquifer and Dismal Backwater is a fine plan for the short term, although in the long term, you'll probably need to upgrade to compete at the higher ranks
I often start with a grey base layer to hide the underlying parts of the card that I wish to paint over