Probably making a stupid mistake, but need someone to point it out to me

That's also how I know I've for sure got the wiring right for this particular model of LED.
......... and my question is why the blue lights aren't turning on when the red ones are on,

The 2nd half of this comment indicates the 1st half is not entirely accurate. All in all,
electronics really is magic, but hooking up Leds is not.