Get Vertex Color from Texture

Hey guys!
Newbie here, have a question.

I need to check if a vertex is a certain color by getting its color from its main texture.

This is what i'm trying to do:

fixed4 tex = tex2Dlod (_MainTex, float4(v.texcoord.xy,0,0)); // Doesn't return the right color

Any help would be appreciated!

 

For some more context: This is my code

Code (CSharp):

1. void vert( inout appdata_full v )
2.         {    
3.             #if !defined(SHADER_API_OPENGL)
4.             float4 tex = tex2Dlod (_MainTex, float4(v.texcoord.xy, 0, 0));
5.             #endif
6.                      
7.             bool test = (tex.r == _ColorT.r)? true:false;
8.                          
9.         }

In the editor, i change the R value of ColorT. No matter what value i use, the test bool is never true.