話不多說，直接程式碼

using System.Collections;

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class TextColorExt : BaseMeshEffect {
private enum Direction
{
Vertical,
Horizontal,
}
[SerializeField]
private Direction mDirection = Direction.Vertical;
[SerializeField]
private Color color = Color.white;
[SerializeField]
private bool isMid = true;
public override void ModifyMesh(VertexHelper vh)
{
if (!IsActive())
return;


if (vh.currentVertCount == 0)
return;

if (isMid) {
List<UIVertex> vlist = new List<UIVertex> ();
for (int i = 0; i < vh.currentVertCount; i+=4) {
UIVertex ver0 = new UIVertex();
UIVertex ver1 = new UIVertex();
UIVertex ver3 = new UIVertex();
UIVertex ver4 = new UIVertex();
vh.PopulateUIVertex (ref ver0, i + 0);
vh.PopulateUIVertex (ref ver1, i + 1);
vh.PopulateUIVertex (ref ver3, i + 2);
vh.PopulateUIVertex (ref ver4, i + 3);


UIVertex ver2 = new UIVertex();
ver2.position = (ver1.position + ver3.position) / 2;
ver2.uv0 = (ver1.uv0 + ver3.uv0) / 2;
ver2.color = color;
ver2.normal = ver0.normal;
ver2.tangent = ver0.tangent;


UIVertex ver5 = new UIVertex();
ver5.position = (ver0.position + ver4.position) / 2;
ver5.uv0 = (ver0.uv0 + ver4.uv0) / 2;
ver5.color = color;
ver5.normal = ver0.normal;
ver5.tangent = ver0.tangent;


vlist.Add (ver0);
vlist.Add (ver1);
vlist.Add (ver2);
vlist.Add (ver3);
vlist.Add (ver4);
vlist.Add (ver5);
}


List<int> tlist = new List<int> ();
for (int i = 0; i < vlist.Count; i += 6) {
tlist.Add (i + 0);
tlist.Add (i + 1);
tlist.Add (i + 2);


tlist.Add (i + 0);
tlist.Add (i + 2);
tlist.Add (i + 5);


tlist.Add (i + 2);
tlist.Add (i + 3);
tlist.Add (i + 4);


tlist.Add (i + 2);
tlist.Add (i + 4);
tlist.Add (i + 5);
}


vh.Clear ();
vh.AddUIVertexStream (vlist, tlist);
} else {
List<UIVertex> vlist = new List<UIVertex>();
vh.GetUIVertexStream(vlist);


if (vlist == null || vlist.Count == 0) 
return;


Color startColr = vlist [0].color;


float leftX = vlist[0].position.x;
float rightX = vlist[0].position.x;


float bottomY = vlist[0].position.y;
float topY = vlist[0].position.y;


for (int i = 1; i < vlist.Count; i++) {
float y = vlist[i].position.y;
if (y > topY) {
topY = y;
} else if (y < bottomY) {
bottomY = y;
}


float x = vlist[i].position.x;
if (x > rightX) {
rightX = x;
} else if (x < leftX) {
leftX = x;
}
}


for (int i = 0; i < vlist.Count; i++) {
UIVertex ver = vlist[i];
float t = 0f;
if (mDirection == Direction.Vertical) {
t = (ver.position.y - bottomY) / (topY - bottomY);
} else {
t = (ver.position.x - leftX) / (rightX - leftX);
}
ver.color = Color.Lerp (startColr, color, t);
vlist[i] = ver;
}


vh.Clear();
vh.AddUIVertexTriangleStream(vlist);
}
}

}

實現結果如下