Ncurses - Issue with A_DIM effect and init_color

Question

Issue

I have recently come across an issue, I can't figure out where it comes from. It appears to be related to an unexpected behavior of the ncurses library when attempting to apply the A_DIM effect on colors other than the first 9 (they don't get dimmed). Furthermore, when initializing a color to one of the first 9 colors (such as init_color(2,0,100,843)), the A_DIM effect seems to result in the dimmed color of the predefined color:

A minimal reproducible example

#include <curses.h>
 

void draw_lines(int y, int c)
{
  char ch = wgetch(stdscr);
  init_pair(c, c, COLOR_BLACK);
  mvhline(y   ,0,'B', COLS);
  mvhline(y+1 ,0,'B', COLS);
  mvhline(y+2 ,0,'B', COLS);
  mvchgat(y  , 0, -1, A_BOLD  , c, NULL);
  mvchgat(y+1, 0, -1, A_NORMAL, c, NULL);
  mvchgat(y+2, 0, -1, A_DIM   , c, NULL);
}

int main()
{
  initscr();
  if (!has_colors()) return -1;
  int i=0, j=0;

  start_color  ( );
  cbreak       ( );
  noecho       ( );
  curs_set     (0);
  mouseinterval(0);
  keypad(stdscr, TRUE);
  refresh      ( );

  for (i=0; i<LINES; i+=3) { 
    draw_lines(i, j);
    j += 1;
  }
  for (i=1; i<LINES/3; i++) {
    init_color(i,0,100,843); // BLUE
    draw_lines(i*3, i);
  }
  endwin();
  return 0;
}

(I am using Alacritty and ncurses-6.4-1)

Question

Is this supposed to happen? and if yes, then how should I approch the initialization of colors, if I want to preserve the ability of the user to customize colors in my app but also keep things sane?

But Why

The reason I care so much is this, where my aproach goes something like this. Meaning that I use an offset so that the user can define custom colors for every individual tui-component, but also be able to have the same color-pattern for all of them if he\she wants so.

Outro

Any idea? Thanks in advance for any help.