How can I create a custom color palette to use in survey question editor?

Hi, I have created a custom theme in Qualtrics to match my company's color palette. I would also like to have certain text appear in a specific color for some questions throughout the survey--while not changing the theme for the whole survey. I change the text through the rich text editor, but every time I need to input the custom hex number because it doesn't show up in the font color options. Do you know if there is a way to add this permanently to the theme (or even to do it once when I enter the survey editor and have it appear again for other questions after doing it once)? Thank you!