Loss of color when converting to open3D

[alek5k]

Describe the bug
When converting to an open3d instance, the color of the point cloud is lost

To Reproduce
Steps to reproduce the behavior:

import open3d
from pyntcloud import PyntCloud

pointcloud = open3d.io.read_point_cloud("MyColorPointCloud.ply")
open3d.visualization.draw_geometries([pointcloud])
# See screenshot below

pyntcloud = PyntCloud.from_instance("open3d", pointcloud)
pointcloud_reconverted = pyntcloud.to_instance("open3d")
open3d.visualization.draw_geometries([pointcloud_reconverted])
# see screenshot below

Expected behavior
The color should be preserved through to_instance call.

Screenshots
First visualization:

Second visualization:

Desktop (please complete the following information):

• OS: Windows 10
• PyntCloud Version: 0.3.1