Blending shaders with EffectsComposer & 3DBlendShader

Questions
1

The code below displays an all white screen. Cannot find any documentation on shader blending. Is there a better approach?
this.renderScene = new RenderPass( this.scene, this.camera );
this.outputPass = new OutputPass();.

    this.renderColor = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, { minFilter: THREE.LinearFilter, magFilter: THREE.LinearFilter, format: THREE.RGBAFormat} );
    this.renderDither = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, { minFilter: THREE.LinearFilter, magFilter: THREE.LinearFilter, format: THREE.RGBAFormat} );

    this.composerColor = new EffectComposer( this.renderer, this.renderColor  );
        this.composerColor.rendertoScreen = false;[.](https://github.com/watchbob-marley-online-full-hd-free)
        this.composerColor.addPass( this.renderScene );
        //this.composerColor.addPass( this.outputPass );

    this.composerDither = new EffectComposer( this.renderer, this.renderDither );
        this.composerDither.rendertoScreen = false;
        this.composerDither.addPass( this.renderScene );
        this.ditherDotShader = new ShaderPass( DotScreenShader );
        this.ditherDotShader.uniforms[ 'scale' ].value = 4;
        this.composerDither.addPass( this.ditherDotShader );
        this.ditherRgbShiftShader = new ShaderPass( RGBShiftShader );
        this.ditherRgbShiftShader.uniforms[ 'amount' ].value = 0.0015;
        this.composerDither.addPass( this.ditherRgbShiftShader );
        //this.composerDither.addPass( this.outputPass );

    this.blendComposer = new EffectComposer( this.renderer );
        this.blendShader = new ShaderPass( BlendShader );
        this.blendShader.uniforms.tDiffuse1.value = this.renderColor; 
        this.blendShader.uniforms.tDiffuse2.value = this.renderDither; 
        this.blendShader.uniforms.opacity.value =   0.5;
        this.blendShader.uniforms.mixRatio.value =  0.5;
        this.blendComposer.rendertoScreen = true;
        this.blendComposer.addPass( this.renderScene );
        this.blendComposer.addPass( this.blendShader );
        this.blendComposer.addPass( this.outputPass );
2

Same question, same answer: