If statement is not accepting my input

Goal: When the user enters in a color not in the list, it should default to gray. If the user chooses a color in the list that color should be used.

What is actually happening: Color is always defaulting to gray.

Plain text example 1: Choose a color: yellow, green, red, purple or gray. User: Blue. Output: Color is gray.

Plain text example 2: Choose a color: yellow, green, red, purple or gray. User: Green. Output: Color is Green.

[CmdletBinding()]
param (

[Parameter(Mandatory=$True, HelpMessage="Choose yellow, green, red, purple or gray")]
[string]$color_select

)

$colors_list = "yellow", "green", "red", "purple", "gray", "random"

if ($color_select -notcontains $colors_list) {

$color_select = "gray"

}


Write-host "The color is: $color_select"