Change container background color from the input it has a textfield.

I am trying to create a container that will change upon the input given on a textfield. Example: If the input on the textfield is 'MX87B', I will always obtain the last # value and that will give the color. For 1 - Red, 2-Green, 3-Blue, 4-..... Disregarding the last digit.

I am really new to flutterflow, so I have try GPT and also some video tutorials, but I am unable to figure it out. I am trying to create it by AppState. Defining the color and the GPT recommends me some code. But I am unable to achieve it. Some guidance would be appreciated.