Editing alpha through a script and animation changes the colour not the transparency?

so i have a material, and a script that gets the alpha and applies the alpha to the material, script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 public class alphatracker : MonoBehaviour
 {
     public Material mat;
     public float alpha;
 
     // Update is called once per frame
     void Update()
     {
         if (mat != null)
         {
             mat.color = new Color(mat.color.r, mat.color.b, mat.color.g, alpha);
         } 
 
         
     }
 }
 

ok and i have an animation that edits this 'alpha' value, from 1 to zero.

so, i'd expect this animation to edit the transparency but instead it just changes the purple to yellow alot. (sorry for the bad quality, the unity file size limit is so low, i had to compress it. and that VEED.IO watermark is me trimming the video using veed because even compressing it was not enough)

so what is the problem??