I've tracked the puzzle down & there are some "Instructions", to wit (partly) -
"Eleven answers are to be entered using a code in which the nth letter of the alphabet is replaced by the nth letter of a 26-letter phrase..."
Sorry, but that's where I step off the train - Wilbo, in future, *please* make sure to post extra instructions, as without them anyone trying to help won't get far, as shown here -
https://www.theanswerbank.co.uk/Quizzes-and-Puzzles/Crosswords/Question1612778.html
where my answer is right, but the letters you've shown are correct for those answers. I'd guess then, that 'yellow' has to be entered using the jiggery-pokery.
If anyone wants the puzzle, it's here (page 50 if you print it) -
https://tinyurl.com/y7ymwg5w