Program stops compiling when I add function to a class

Question

I have a virtual base class, base_class, that uses as attribute a class type object of class colours. From the virtual base class, I derived another class, derived_class.

The debugger doesn't show any errors, but my program is not compiling. I found that if I remove the virtual function declaration in the base_class, the whole program compiles just fine. Why is this? I wanted to keep the virtual function, how can I do it?

Here is the code:

class colours {
protected: 
    std::vector<double> colour1, colour2; 
public:
    colours() {std::cout << "Calling colours default constructor" <<std::endl;}
    colours(std::vector<double> c1, std::vector<double> c2) : colour1{c1}, colour2{c2} {} 
    ~colours(){}
};

class base_class {
protected:
    std::string name{"unnamed"};
    colours col;
public:
    base_class() {std::cout << "Calling base default constructor" <<std::endl;}
    base_class(std::string const n, colours const c) : name{n}, col{c} {} 
    virtual ~base_class(){} 
    
    virtual void do_something();
};

class derived_class : public base_class {
public:
    derived_class() : base_class() {std::cout << "Calling derived default constructor" <<std::endl;} // This is what makes my code not work
    derived_class(std::string const n, colours const c) : base_class{n, c} {} 
    ~derived_class(){}

    void do_something();
};

void derived_class::do_something() {
    std::cout << "I am doing something";
}

int main() {
    derived_class test;
    return 0;
}