First one on July 12,2018
https://www.today.com/style/first-lady-melania-trump-stuns-floaty-yellow-gown-state-dinner-t133162
Second one June 26,3017
https://indianexpress.com/article/lifestyle/fashion/melania-trump-greets-pm-narendra-modi-in-a-cheery-yellow-floral-print-emilio-pucci-gown-4724205/
Digging on other two and there is a fifth one.
Sorry, floral one was third one. Still digging
Second one May 4,2017
https://www.eonline.com/news/848707/melania-trump-stuns-in-yellow-dior-gown-at-her-and-donald-trump-s-dinner-with-australian-pm
Fourth one June 18, 2019
https://dailycaller.com/2019/06/18/melania-trump-yellow-jumper-rally-florida/
Fifth one August 24, 2019
https://www.today.com/style/melania-trump-arrives-france-wearing-tie-dye-denim-dress-t161285
Floral print one was in 2017 not 3017, did not travel to the future.
At least two other times she has worn yellow. The most recent visit to UK when she wore the yellow cape and she wore pale yellow coat and dress when meeting with Putin in Helsinki.
My post was in reference to a thread about Melania.