Can you introduce and name NPC as color and circle them later with your circles? Just like how you introduce tech with color.
Could the same limitations of color tech apply to color NPC, so that you can interact with them as color?
I am asking because it would be cool to add color NPC with names in some scenes.
Sure, why not?
Some thoughts:
Color trumps color 
Circles doesn’t (necessarily) establish the existence of an NPC, but rather their disposition toward you when you find them.
I think if I were GMing BE and someone wanted to name-drop during a color scene, I’d be hard-pressed to stop the player from doing so. I think I’d say “whoa, time to roll” as soon as the player started angling for meaningful non-color advantage in the game fiction.
Also, it establishes that you can find them here and now.
You can absolutely use color to establish “There is a fellow named James ‘Jimmy Hat’ Hatfield, and he is a forger.” When it comes time to find him again and get him to do some forging, you might find that he’s gone underground and you can no longer locate him, or that he’s pissed about something, or just that he wants a lot more money than you’d hoped.
Further, there are some Circles tests where the whole intent of the test is to find some certain dude. “I’m looking for your ex-lover.” If that person exists and is contactable, I have an advantage. In those kinds of cases, unless the GM has in her pocket an interesting consequence if the Circles test is delayed, it’s not legit to create that person in color. I would generally reserve coloring in NPCs for either NPCs who will never matter, or those whose importance will be related to stuff they’ll do or give, so that a later Circles test can be used to determine if they’re willing to do or give those things.
Good point about intents not related to future tests or use of resources (like wanting to find a ex-lover). I guess the line can be blurry sometime.
It just that beside relations, peoples and the world feel blank around our characters.
Like my anvil character, I am part of a squad, and I would like to include my squad members in my color scenes without having to circle them for nothing. Kind of foreshadowing for later.
For example I described a scene where my squad was training with stun batons to introduce my stun baton as color. I wanted to color the squad member with whom I was practicing but when I played the scene I left him as a blank and I dint talk with him since I dint know if it was ok and I dint want to spend a circle test on this.
Oh, yeah, I totally make up (color) people all the time – as do my players. Totally cool, get down with your bad self. The GM will make you roll if you want to establish something more permanent in the fiction.
Also, you have an affiliation (or something) that represents your squad, right? That affiliation means that there is a squad with people in it. It doesn’t give those people particular talents or skills or resources, nor does it grant you access to those people at any particular time (you need to test Circles for those things) but just adding a dude with a name that you can talk to? That would be kosher anyhow, but when it’s an affiliated dude, it’s unassailable.