Sorting bugs with custom UI shader

I wanted to be able to recolor some of my UI images using color picker and a channel mask. So I created the new Unlit shader with this recolor by mask functionality. But after I applied said shader to UI Image component, it became occluded by background Sprite renderers (it is 2d game). I had to settle with no shaders and using pre-colored pictures. Anything that needs to be added to shader code to avoid it?

Shader "Unlit/PowerupMeterColored"
{
    Properties
    {
        _MainTex ("cell grayscale", 2D) = "white" {}
        _CellColor ("cell color", Color) = (0,0,1,1)
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _CellColor;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                return col + (1.0 - col.r)*_CellColor;
            }
            ENDCG
        }
    }
}

Bump: same situation is when sprite is assigned custom material created from Surface shader