Why system("color 3") is "global"? - c++

Question

Code:
int print()
{
system("color 2"); //paint the "one"
std::cout << "one" << std::endl;
}
int main()
{
print(); //prints "one"
system("color 3"); //paint the "two"
std::cout << "two" << std::endl;
return 0;
}
I'm a newbie programmer, and I want to write a simple code which prints text in different colors. The thing is, when I compile it, cout “one” and “two” are the same color as I don't expect. However, when I change the color in int main(), cout “one” take color from int main() forgetting about the “color2” from function print().
And my question is, how to avoid that “global” system(“color 3”)? What exactly happened? Is it a good method to color a text?

Answer 1

I want to write a simple code which prints text in different colors.
Your question is not C++ related and is operating system (and hardware) specific. Some computers don't have color screens (and some don't have any screens at all, but still provide a standard conforming C++ implementation, e.g. some web, network, internet server, IoT device, etc...)
We don't know what color is or does. It could even be some of your private program somewhere in your $PATH (used by the command processor working for system). BTW, practically speaking, running an external program to simply change colors is inefficient.
Standard C++ does not know about colors at all. Only about standard streams.
Maybe your program is outputting on some terminal capable of ANSI escape codes (but you need to check that - and with command pipelines or redirections your stdout or std::cout is not even a terminal!). Then you might use something like
#define ESCAPE_BOLD "\033[1m"
#define ESCAPE_NORMAL "\033[0m"
and later
std::cout << "Here is something " << ESCAPE_BOLD << "in bold"
<< ESCAPE_NORMAL << std::endl;
I leave you to find out the escape sequence for red.
Maybe you want to code some GUI application. Then use a widget toolkit like Qt.
Perhaps you want to code a textual interface. Then consider some library for that, e.g. ncurses.
Maybe you want some web interface (so learn more about web technologies), then use some HTTP server library like Wt or libonion.

Answer 2

I assume your color refers to builtin in windows cmd.exe (or DOS builtin). If so, the documentation explains it clearly
The COLOR command will change the color of all the text in the window.
https://ss64.com/nt/color.html
So what happens is
You change the window color to green
Print "one"
Change the window color to aqua - this changes also already printed "one"
Print "two"
You can check if I'm right by adding some delay between changing color (like std::cin.get())