### 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)

for (int i = 0; i < 4; i++) {
			state.instance_data_array[r_index].modulation[i] = 0.0;
			state.instance_data_array[r_index].ninepatch_margins[i] = 0.0;
			state.instance_data_array[r_index].src_rect[i] = 0.0;
			state.instance_data_array[r_index].dst_rect[i] = 0.0;
			state.instance_data_array[r_index].lights[i] = uint32_t(0);
		}
		state.instance_data_array[r_index].color_texture_pixel_size[0] = 0.0;
		state.instance_data_array[r_index].color_texture_pixel_size[1] = 0.0;
		state.instance_data_array[r_index].pad[0] = 0.0;
		state.instance_data_array[r_index].pad[1] = 0.0;
		state.instance_data_array[r_index].lights[0] = lights[0];
		state.instance_data_array[r_index].lights[1] = lights[1];
		state.instance_data_array[r_index].lights[2] = lights[2];
		state.instance_data_array[r_index].lights[3] = lights[3];
		state.instance_data_array[r_index].flags = base_flags | (state.instance_data_array[r_index == 0 ? 0 : r_index - 1].flags & (FLAGS_DEFAULT_NORMAL_MAP_USED | FLAGS_DEFAULT_SPECULAR_MAP_USED)); 
		Color blend_color = base_color;
		GLES3::CanvasShaderData::BlendMode blend_mode = p_blend_mode;
		if (c->type == Item::Command::TYPE_RECT) {
			const Item::CommandRect *rect = static_cast<const Item::CommandRect *>(c);
			if (rect->flags & CANVAS_RECT_LCD) {
				blend_mode = GLES3::CanvasShaderData::BLEND_MODE_LCD;
				blend_color = rect->modulate * base_color;
			}
		}
		if (blend_mode != state.canvas_instance_batches[state.current_batch_index].blend_mode || blend_color != state.canvas_instance_batches[state.current_batch_index].blend_color) {
			_new_batch(r_batch_broken);
			state.canvas_instance_batches[state.current_batch_index].blend_mode = blend_mode;
			state.canvas_instance_batches[state.current_batch_index].blend_color = blend_color;