AE Controller for changing layer into specific colours
Use a dropdown. Select Dropdown Expression Control from Effects&gt;Expression Controls and hit edit to input the colour names.

Then use a switch to deal with the four possible choices.
let colourChoice = Math.round(thisComp.layer(&quot;White Solid 1&quot;).effect(&quot;Dropdown Menu Control&quot;)(&quot;Menu&quot;));
switch (colourChoice){
    case 1 : [7, 250, 198, 255]/255.0;
        break;
    case 2 : [252, 12, 119, 255]/255.0;
        break;
    case 3 : [0, 0, 0, 0];
        break;
    default:  [1, 1, 1, 1];

}
N.B.:

Math.round on the firstline is to convert the numeric result returned from the dropdown to an integer, I'm not sure what kind of numerical value is returned from a dropdown, but just using let colourChoice = thisComp.layer(&quot;White Solid 1&quot;).effect(&quot;Dropdown Menu Control&quot;)(&quot;Menu&quot;) doesn't work.

Colours in expressions are four-dimensional RGBA arrays, because even if they don't use alpha they need a value for alpha.

And finally the / 255 after the array is to convert the 0-255 RGBA values into 0-1.0 floating point values for colour. You could do the maths beforehand, but it's more legible like this.