The leaves are shiny and either pale or dark green when fresh.
Utazi is available frozen in North America and Europe at some African food stores. The leaves will go dark green when frozen.
You use Utazi in small amounts, somewhere in the order of just 1 tablespoon maximum for a pot of soup. You chop it up, as you would other herbs.
Rocket, rapini or bitterleaf (though bitterleaf, being another African herb, is likely just as hard to get).
Called “Madumaro” in Nigeria.