Colored Keys

I'm sorry if this has been asked before but I've done a search here and found something about colored diamonds.

Next to the field of the tables in Heidi I see a yellow key, a green key and sometimes a red key.

Could someone please tell me what the colors mean?

Thanks in advance and have a good day.

• yellow = primary key
• red = unique key
• green = normal index
• dark blue = fulltext index
• light blue = spatial/geometry key

The key type is also displayed in the "Indexes tab":

Thank you very much!