How to make projector shaders override each other?

Hi again.

I asked a question previously here, where @Fattie directed me to trying out lights to solve my problem. I didn't figure out how to do it, but I got really close to what I want using Projectors.

Basically I want to project a color in the shape of a circle, which will grow until it tints the entire environment.

This is what I have so far:

The problem is that I want them to override each other (in this case blue should override red) instead of blending their alpha channels.

Here is the shader I'm using for the projectors:

 Shader "Custom/MyProjectorShader" {
   Properties {
      _Color ("Main Color", Color) = (1,1,1,1)     
      _ShadowTex ("Cookie", 2D) = "" { TexGen ObjectLinear }
      _FalloffTex ("FallOff", 2D) = "white" { TexGen ObjectLinear }
   }
   Subshader {
      Tags { "Queue" = "Overlay" }
      
      Pass {
         ZWrite Off
         AlphaTest Greater 0
         Offset -1, -1
         ColorMask RGB
                 
         Blend SrcAlpha OneMinusSrcAlpha
         
         
        // Color [_Color]
         
         SetTexture [_ShadowTex] {
             constantColor [_Color]
             combine texture*constant
             Matrix [_Projector]
         }
         
         SetTexture [_FalloffTex] {
            constantColor (0,0,0,0)
            combine previous lerp (texture) constant
            Matrix [_ProjectorClip]
         }
      }
   }
 }

Their materials' Alpha is set to 200. If I set them to 255 this is the result:

I tried tinkering with the shader, but to no avail. I'm quite new to Shader programming. If someone could give me a hint, would me much appreciated. =)

Thanks.