Basing world coloring works.

materials/GrassNoiseMaterial.tres

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+[gd_resource type="StandardMaterial3D" load_steps=4 format=3 uid="uid://bg3dawo5kkosg"]
+
+[ext_resource type="Material" uid="uid://c60s78p4g17ye" path="res://materials/WorldColoringMaterialPass.tres" id="1_3d3it"]
+
+[sub_resource type="FastNoiseLite" id="FastNoiseLite_wonuc"]
+noise_type = 0
+frequency = 0.014
+fractal_lacunarity = 3.0
+
+[sub_resource type="NoiseTexture2D" id="NoiseTexture2D_iklfu"]
+width = 32
+height = 32
+seamless = true
+seamless_blend_skirt = 0.857
+normalize = false
+noise = SubResource("FastNoiseLite_wonuc")
+
+[resource]
+next_pass = ExtResource("1_3d3it")
+albedo_color = Color(0.113725, 0.431373, 0.266667, 0.933333)
+albedo_texture = SubResource("NoiseTexture2D_iklfu")
+uv1_scale = Vector3(20, 1, 20)
+uv1_triplanar = true
+texture_filter = 0

materials/WorldColoringMaterialPass.tres

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+[gd_resource type="ShaderMaterial" load_steps=3 format=3 uid="uid://c60s78p4g17ye"]
+
+[ext_resource type="Shader" path="res://materials/shader/WorldColoring.gdshader" id="1_ashe5"]
+[ext_resource type="Texture2D" uid="uid://b2c7rc40v7wfl" path="res://assets/textures/test_world_color_texture.png" id="2_60odu"]
+
+[resource]
+render_priority = 1
+shader = ExtResource("1_ashe5")
+shader_parameter/world_color_texture = ExtResource("2_60odu")

materials/shader/WorldColoring.gdshader

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+shader_type spatial;
+
+uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_nearest;
+uniform sampler2D world_color_texture : hint_default_black, repeat_disable;
+
+void vertex() {
+	// Called for every vertex the material is visible on.
+}
+
+void fragment() {
+  vec4 projected_coords = INV_VIEW_MATRIX * vec4(VERTEX, 1.0);
+	
+  vec4 currentColor = textureLod(screen_texture, SCREEN_UV, 0.0);
+  vec4 worldColor = textureLod(world_color_texture, projected_coords.xz * 0.01 + vec2(0.5), 0.0);
+  vec3 colorToLuminance = vec3(0.2126, 0.7152, 0.0722);
+  ALBEDO = vec3(dot(currentColor.rgb, colorToLuminance) * 0.4) + 0.2 * currentColor.rgb + 0.4 * worldColor.rgb;
+}
+
+//void light() {
+	// Called for every pixel for every light affecting the material.
+	// Uncomment to replace the default light processing function with this one.
+//}