multisite favicons

I am having a problem with setting site specific favicons in multisite installations using the B7 theme, which contains subthemes for Brown and Green.

When you use the shortcut icon settings in the configuration part of Settings>Themes, it works for the main B7 theme on the primary site and any secondary sites using the main B7 theme. This setting renames the favicon B7_favicon.ico and sends it to the Files folder. This works.

However, when you use the shortcut icon settings for B7 Green, it creates a file called B7 Green_favicon.ico and sends it to the same Files folder. This does not work. The same is true for B7 Brown.

I run a number of multiple sites using variants of the B7 theme. The shortcut icon settings always work for the primary site and the main B7 theme, but never for the additional sites using the same code base that use B7 Green or Brown. So, this is a general problem.

Is this a quirk of the B7 theme, or is there something else still need to do?

I would appreciate any suggestions.