### 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)

RenderingServer::CanvasItemTextureFilter texture_filter = p_item->texture_filter == RS::CANVAS_ITEM_TEXTURE_FILTER_DEFAULT ? state.default_filter : p_item->texture_filter;
	if (texture_filter != state.canvas_instance_batches[state.current_batch_index].filter) {
		_new_batch(r_batch_broken);
		state.canvas_instance_batches[state.current_batch_index].filter = texture_filter;
	}
	RenderingServer::CanvasItemTextureRepeat texture_repeat = p_item->texture_repeat == RS::CANVAS_ITEM_TEXTURE_REPEAT_DEFAULT ? state.default_repeat : p_item->texture_repeat;
	if (texture_repeat != state.canvas_instance_batches[state.current_batch_index].repeat) {
		_new_batch(r_batch_broken);
		state.canvas_instance_batches[state.current_batch_index].repeat = texture_repeat;
	}
	Transform2D base_transform = p_canvas_transform_inverse * p_item->final_transform;
	Transform2D draw_transform; 
	Color base_color = p_item->final_modulate;
	uint32_t base_flags = 0;
	Size2 texpixel_size;
	bool reclip = false;
	bool skipping = false;
	
	uint32_t lights[4] = { 0, 0, 0, 0 };
	uint16_t light_count = 0;