LCD Post Effect: https://www.shadertoy.com/view/ldBfDd

lcd_post_effect

shader_type canvas_item;

uniform float pb : hint_range(0, 1.0) = 0.4;
uniform float sclV : hint_range(0, 1.0) = 0.25;

void fragment() {
	vec2 uv = FRAGCOORD.xy / SCREEN_PIXEL_SIZE.xy;
	//or uv = SCREEN_UV; - it's look good!
	
	vec4 texColor = texture(SCREEN_TEXTURE, uv);
	
	vec4 lcdColor = vec4(pb, pb, pb, 1.0);
	
	int px = int(mod(FRAGCOORD.x,3.0));
	if (px == 1)
		lcdColor.r = 1.0;
	else if (px == 2)
		lcdColor.g = 1.0;
	else lcdColor.b = 1.0;
	
	if (int(mod(FRAGCOORD.y, 2.0)) == 0)
		lcdColor.rgb = vec3(sclV, sclV, sclV);
		
	COLOR = texColor * lcdColor;
}