Transparent object changes colors when camera changes the angle

In the scene, I have translucent objects which are set to 20% occupancy in black color.
After I embedded the SD model to our website, the color looks not black, but white-ish.
And when I rotate the camera to different angles, the objects can be presented as black translucent again.
I was wondering the reasons for this.
Is it related to lighting? Or the material?

In the model, the lady and cat should be in black color.

But it is showing in grey-ish color. And sometimes, for both of them, sometimes just one of them, based on the angle of camera.

I looked at your model and could not reproduce this issue. Which device and browser are you using? Did you test using other devices and/or browsers?

@mathieu1 Thanks for your reply.
I tested on multiple devices, with different desktops, laptops, with different browsers, Chrom, Firefox, Microsoft Edge. So far alll of them have the exact same issue.

Please send me a link to the specific model, I must have looked at another one.

This issue happens in the version 2 of the viewer and is a known issue with the way this version deals with transparency. It is fixed in version 3 of the viewer.