Demo 42 - Varying color

Shader "Custom/VaryingColor"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _RampTex ("Ramp texture", 2D) = "white" {}
        _Speed ("Speed", Range(1, 10)) = 1
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag

            #include "UnityCG.cginc"

            sampler2D _MainTex;
            sampler2D _RampTex;
            float _Speed;

            fixed4 frag (v2f_img i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                return tex2D(_RampTex, fixed2(col.r + _Time.x * _Speed, 0.5));
            }
            ENDCG
        }
    }
}