Let me begin by saying it would be great if newly created options were not automatically assigned colors at all; as others have reported it adds another step to go in and remove it if you want all your dropdowns to appear uniform.

But as of very recently, the ability to even remove the auto-assigned color to dropdown options has disappeared.

At the time of writing this, I am now only able to reassign the option a different color. For dropdowns where I have hundreds of pre-existing "colorless" options - by this I mean that their backgrounds are blank and actually change to match your light or dark mode choice - now any new options I create look different and cannot be adjusted to match the old ones.