What is the significance of this? There are locations in Whiterun and at Dragonreach with these clothes in dressers. When searching, these items have red lettering.

Take them, it's stealing.

The red letters mark stealable items, which are items that you don't own. While all the items in an NPC's pocket are red, some, usually lower-value things in their houses are takeable after befriending them (raising the disposition). For example, become Thane of Whiterun and most things in Dragonsreach will be in white letters.

Got it. Thanks all.