Not a Problem
I made a simple custom tool (to build a square), and gave it an icon (screensnipped from a geogebra file). It looks fine in Classic 5 (right), but when uploaded (left) the tool has a strange colour. See screenshot attached.
Do I need to make tool background transparent? Use a different file type?
Image file used is a jpg and is attached.
The same problem 
Try as PNG (JPG is for photos)
Online link: https://www.geogebra.org/m/ctmhhxje
Try as PNG (JPG is for photos)
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