My hair also grows super slowly. It is annoying. Cutting off a few inches is a commitment.
Coloring you hair does cause damage. But you have to decide which damage you are willing to do to your hair. Hair color is worth it to me. I've found that stopping other things (sulfates, brushing, etc.) made a huge difference in my hair. The color damage is less of a big deal for my hair.
If you color will hold for 6 months at a time, that suggest it is not porous. It does depend on what type of color you are using, and if you are matching your natural color, going darker, or lighter.
The easiest way to figure out hair porosity, is to go to livecurlylivefree.com. The have a service call the curl wizard. You send in your hair and they tell you texture, elasticity, and porosity. (13$ish???) For around 20$ish they will recommend products that will work for your hair.
Protein will go a long way to temporarily repair hair. Since you have very fine hair, protein will be your friend no matter what the porosity. One of the main reasons to figure out porosity is to get an idea of how much protein to add. Since fine hair needs protein anyway, it is less important to know your porosity.
I really like IAgirl's gelatin protein treatment.
PT recipe - as promised
Other CG PTs are nexxus emergencee, joiko k-pac (and sally beauty knock off, has mineral oil), ion effective care (sally's), aphogee 2 minute and aphogee 2 step (sally's, step 2 in 2 step has mineral oil).
Mineral oil can make some hair oily an weigh it down. If you want to experiment with products that contain this, I'd suggest trying a small section/curl first to see how it goes.
Follow a PT with a DT or moisturizing conditioner. After you rinse out the PT it may feel rough or hard. This is normal. The DT will make it feel nice again.
Since you have fine hair, Ecostyler gel might work for you. It is a harder hold gel with protein. It is 3-4$ per tub at sally beauty. CVS has it also. I like a little harder hold, so I use BRHG over the top. The one I have is Ecostyler Krystal.
I'd classify you as 2a/2b, but I'm really bad at that kind of thing. With the nc method, you are definitely 2a.
Also, if you are interested in trying the boutique brands people mention here (spiral solutions, curl junkie, darcy's botanicals, etc.), the member Kathymack sells samples. Click on the fotki in her siggi. That way you can try before you buy.
(a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers