Disable fields from a dropdown

I have a dropdown with the color fields:

Blue
red
green
black

I want a condition, which disables only red. That is, this dropdown shows me only blue, green and black

Example:
IF ([Number] = month ([date]), all dropdown, or (blue, green and black))

Can you understand me?

I need help, please

Hi @Eduardo_dos_Santos_C,

In general , you may use following expression in the valid_if of the dropdown column.

IF ([Number] = month ([date]), {red, blue, green, black}, {blue, green and black})