### Godot version

4.0 beta 17

### System information

Windows 10

### Issue description

Setting the color attribute in ParticleProcessMaterial for GPUParticles2D does not work with compatibility renderer
(works with forward+)

### Steps to reproduce

Set renderer to compatibility
Create a GPUParticles2D
Add ParticleProcessMaterial and set Color attribute (creating a particle shader and setting the `COLOR` is the same)


### Minimal reproduction project

[Particle2DColor.zip](https://github.com/godotengine/godot/files/10678236/Particle2DColor.zip)

GLES3::TextureStorage *texture_storage = GLES3::TextureStorage::get_singleton();
	if (p_texture == RID()) {
		p_texture = default_canvas_texture;
	}
	GLES3::CanvasTexture *ct = nullptr;
	GLES3::Texture *t = texture_storage->get_texture(p_texture);
	if (t) {
		
		if (!t->canvas_texture) {
			t->canvas_texture = memnew(GLES3::CanvasTexture);
			t->canvas_texture->diffuse = p_texture;
		}
		ct = t->canvas_texture;
	} else {
		ct = texture_storage->get_canvas_texture(p_texture);
	}
	if (!ct) {
		
		_prepare_canvas_texture(default_canvas_texture, p_base_filter, p_base_repeat, r_index, r_texpixel_size);
		return;
	}