Honor Holly 3 is available in 3 different colors - Black, Gold and White.
To add watermark, go to Camera App > Go to Camera Menu > Go to Watermark and click your picture.
If you want to add watermark on the already captured pictures, Go to Gallery > Select the picture where you want to add watermark > Click on Edit > Select Watermark option.
No. Honor Holly 3 do not support OTG.