XnView Software

I just starting using the software for sorting my photos and I have to say its been great, the only suggestion I have so far is that you should be able to add multiple color labels to a single photo and create more color labels if you'd like to. For example I want to label a photo to look at again later and to post to Instagram, but that is two labels.

A great example of this is like Mac Finder, How I can create new tags and put multiple tags on a single photo.

Iptc and xmp standards do not allow multiple colors labels to be assigned to a single picture.
You can use keywords / categories instead ...

See howto
viewtopic.php?p=179720#p179720 paragraphs 2 and 4