HTML color to std::byte

Color.cpp

#include <iostream>
#include <cstddef>
#include <algorithm>
#include <string>
#include <exception>

struct Color{
    Color(const std::string& html_col)
    {
        if (html_col.length() < 9){
            throw std::exception("String too short");
        }
        r = std::byte(std::stoi(html_col.substr(1,2), nullptr, 16));
        g = std::byte(std::stoi(html_col.substr(3,2), nullptr, 16));
        b = std::byte(std::stoi(html_col.substr(5,2), nullptr, 16));
        a = std::byte(std::stoi(html_col.substr(7,2), nullptr, 16));
    }

    std::byte r;
    std::byte g;
    std::byte b;
    std::byte a;
};


int main(int argc, char** argv)
{
    Color c(argv[1]);
    std::cout << "Color is RGB("<< std::to_integer<int>(c.r) << ", "
                                << std::to_integer<int>(c.g) << ", "
                                << std::to_integer<int>(c.b) << ", "
                                << std::to_integer<int>(c.a) << ")"
                                << std::endl;
    return 0;
}