Kill two enemies with one bullet

I found a tower weapon unlock list here:

Radio Towers reward you with free weapons and items and they also unlock nearby Supply Drop missions. You’re rewarded with free weapons based on the amount of Radio Towers you’ve unlocked, not by the specific Radio Tower itself. This means that if you want a specific weapon, you can just go for the quickest/easiest route to get there, without having to do a specific tower the other side of the map. The below weapons have been placed into categories along with how many Radio Towers you need to get them for free.

Handguns

• 1911

• 6P9

• .44 Magnum – Requires 11 Radio Tower unlocks.

• D50 – Requires 12 Radio Tower unlocks.

SMGs

• Skorpion – Requires 2 Radio Tower unlocks.

• A2000 – Requires 5 Radio Tower unlocks.

• MP5 – Requires 9 Radio Tower unlocks.

• BZ19 – Requires 14 Radio Tower unlocks.

• Vector .45 ACP – Requires 12 Radio Tower unlocks.

Shotguns

• M133 – Requires 5 Radio Tower unlocks.

• 1887 – Requires 4 Radio Tower unlocks.

• SPAS-12 – Requires 13 Radio Tower unlocks.

Assault Rifles

• AK47 – Requires 2 Radio Tower unlocks.

• STG-90

• F1 – Requires 8 Radio Tower unlocks.

• MS16 – Requires 10 Radio Tower unlocks.

• P416 – Requires 15 Radio Tower unlocks.

• ACE – Requires 13 Radio Tower unlocks.

• Bushman – Signature Weapon. Requires 18 Radio Tower Unlocks

Sniper Rifles

• SVD – Requires 3 Radio Tower unlocks.

• M-700 – Requires 6 Radio Tower unlocks.

• Z93 – Requires 15 Radio Tower unlocks.

LMG’s

• PKM – Requires 4 Radio Tower unlocks.

• U100 – Requires 7 Radio Tower unlocks.

• MKG – Requires 14 Radio Tower unlocks.

Launchers

• RPG-7 – Requires 6 Radio Tower unlocks.

• GL-94 – Requires 8 Radio Tower unlocks.

Specials - Repair Tool – Requires 2 Radio Tower unlocks.

• Flare Gun – Requires 7 Radio Tower unlocks.

• Recurve Bow – Requires 3 Radio Tower unlocks.

• Flamethrower – Requires 5 Radio Tower unlocks.

From what I can gather, the relics only put points towards the dots and when you complete the story and the relics and purchase every skill, then it completes it. As you progress through the story, it unlocks the wave like thing at the bottom above the larger 2 sharks, spider and heron. Then, later the story unlocks the tree and the vines beside it. and the mask demon in the middle. I beat the game and only thing I have yet to unlock is the 2 wings at the top and all the dots that trail up to it. Which means I need all the relics to get the wings up top.

Edit: The blue you circled is in fact, from the main story. also right above the middle with the 2 faces is a tree, the tree is from another main story quest. All the rest which you labeled in red and yellow are from skill unlocks that you buy with skill points. when you spend points in spider, it goes towards spider art work etc. The relics only give those dots that you circled in green. I believe that when you get all the relics/ collectibles that you get the 2 final "wings" up top, As you can see, each dot represents 1 relic. Everything else is via main story/ spent skill points towards the animal type. basically that means each line of dots that lead up to the top Shark picture on each side equals 60 relics. since there are 120 relics in all and 2 sides. The memory cards may also play part in the tattoo. Maybe part of the line up top above the wings.

edit #2. Relics only unlock the dots and the wings at the VERY top above the heron's. I know this because I -maybe- collected 5 relics before I beat the game and everything was colored in besides the dots and the 2 wings up top. Right now I am sitting at 24 and the dots, which I counted are 24, is right above the head of the seagull looking icon just above the wave that you highlighted in blue. Now, you do of course get XP from the relics and you might've spent points before looking at it again and thought that, but I was too lazy to get the relics and focused mainly on the story. I could probably show you a picture? Since you have more relics than I do you can see the difference.