Because there are so many now up for new shapes for their keys,
here are some guidelines how to the SVG graphic must look like
to meet production requirements.
When you do your SVG, then don't think of colors. Just think of the shape which has to be on the key.
If you make a yellow on black key, the black stuff in your file will be yellow in production, all the transparent stuff is the black base-material of the key.
On a 1x1 key, the maximal size a shape on the key can have, is 9.04mm wide and 10.84mm high.
