Three types of cc:
1. The creator has just recoloured something that is in one the DLC packs, i.e. it's an EA item to begin with. In that case, you already have the 'mesh' ingame so don't need to download anything other than the cc. For example, this creator here has just recoloured an EA hair, so you would download just this file and you're good to go: http://noodlescc.tumblr.com/post/170588366044/february-6th-update-hair-recolor-we-got-a-new-hair
2. The creator has made a brand-new piece of cc, creating their own 'mesh'. In that case, when you download that item of cc, the file will already include the mesh so no need to download anything extra. For example, this creator here has created a new piece of cc, mesh included, so you'd be good to go: https://www.patreon.com/posts/hani-hairs-18023149
3. The creator has recoloured a piece of cc made by somebody else. In 90% of cases like this, in order for the cc to actually be usable in your game you will need to download the recolour PLUS the original mesh by the person who first made the cc. Often, you'll find a link to this original mesh along with the recolour. For example, this creator has recoloured a piece of cc made by somebody else so you'd need the new cc and its original mesh: i.e. here for the new cc: https://auntiegame.tumblr.com/post/172347488945/hannah-hair-recolored-in-the-witching-hour
And here for the original cc, i.e. the 'mesh': https://simblob.weebly.com/hannah.html
So in cases like this, you'll be downloading two files.
Does that make sense?