"Use confidence probability in decision tree result to categorize prediction"

Hi Experts,

I wanted to use the result of decision tree's confidence(1) variable and create a new categorical variable because the end user does not want to see probability, instead, they want to see "RED" if confidence(1) is >0.9, "Yellow" is confidence(1) is between [0.6-0.8].

I was not able to use Generate attribute as the variable confidence(1) does not show up is the list of available variables(attributes).
Is there any other way that I can generate a new variable with a categorical variable?
Any help/suggestion are highly appreciated