If you just want to see the colors in action, here's some some JavaScript you co...

If you just want to see the colors in action, here's some some JavaScript you could run with Deno:

    const encoder = new TextEncoder();

    function csi(text, ... args) {
        const filt = args.filter(xx => xx !== null);
        const output = "\x1b[" + filt.join(";") + "m" + text;
        Deno.stdout.writeSync(encoder.encode(output));
    }

    csi("True Color RGB:\n");
    for (let ii = 0; ii<32; ++ii) {
        for (let jj = 0; jj<64; ++jj) {
            const fg_rr = jj*4;
            const fg_bb = ii*8;
            const fg_gg = (fg_rr + 3*fg_bb)>>2;

            const bg_rr = 255 - ii*8;
            const bg_gg = 127;
            const bg_bb = 255 - jj*4;
            csi("+",
                38, 2, fg_rr, fg_gg, fg_bb,
                48, 2, bg_rr, bg_gg, bg_bb,
            );
        }
        csi("\n");
    }