The color like Black/Beige is apparently not correct it should be something like Black or Beige.
In case it will help any others looking to change the default delimiter for custom attributes:
Google Merchant Center product spec says multiple colors (and materials) should be separated with forward slash instead of comma, and you can include at most three values.
Our products have these as custom attributes, which are exported as a comma-separated list, by default. The comma can be replaced with a forward slash by using the Value Editor provided in the Feed Editor. Use the “edit values” link at the end of the attribute row to access the “and change values” options, where you can choose the “Replace” operation and supply input parameters , (include the trailing space) and / for all products.
