#include <X11/Xlib.h>

#define NCOLORS 1400

int main(void)
{
	Display *dpy = XOpenDisplay(0);
	int screen = DefaultScreen(dpy);
	Colormap cmap;
	XColor colors[NCOLORS];
	int i;
	for(i = 0; i < NCOLORS; ++i)
	{
		colors[i].pixel = i;
		colors[i].red = colors[i].green = colors[i].blue = i * (65535 / (NCOLORS - 1));
		colors[i].flags = DoRed | DoGreen | DoBlue;
	}
	cmap = XCreateColormap(dpy, RootWindow(dpy, screen), DefaultVisual(dpy, screen), AllocNone);
	XStoreColors(dpy, cmap, colors, NCOLORS);
	XCloseDisplay(dpy);
	return 0;
}