### 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)

GLuint new_buffers[3];
	glGenBuffers(3, new_buffers);
	
	glBindBuffer(GL_ARRAY_BUFFER, new_buffers[0]);
	glBufferData(GL_ARRAY_BUFFER, data.max_instance_buffer_size, nullptr, GL_STREAM_DRAW);
	
	glBindBuffer(GL_UNIFORM_BUFFER, new_buffers[1]);
	glBufferData(GL_UNIFORM_BUFFER, sizeof(LightUniform) * data.max_lights_per_render, nullptr, GL_STREAM_DRAW);
	
	glBindBuffer(GL_UNIFORM_BUFFER, new_buffers[2]);
	glBufferData(GL_UNIFORM_BUFFER, sizeof(StateBuffer), nullptr, GL_STREAM_DRAW);
	state.current_data_buffer_index = (state.current_data_buffer_index + 1);
	DataBuffer db;
	db.instance_buffers.push_back(new_buffers[0]);
	db.light_ubo = new_buffers[1];
	db.state_ubo = new_buffers[2];
	db.last_frame_used = RSG::rasterizer->get_frame_number();
	state.canvas_instance_data_buffers.insert(state.current_data_buffer_index, db);
	state.current_data_buffer_index = state.current_data_buffer_index % state.canvas_instance_data_buffers.size();
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindBuffer(GL_UNIFORM_BUFFER, 0);
}
void RasterizerCanvasGLES3::_allocate_instance_buffer() {