I'd originally thought that the LED backlighting wouldn't go well with the vintage style of the keyboard, but to my surprise, after I decided to turn on the LED, I found that selecting the blue backlighting pleasantly enhanced the look of the green keys, especially after I reduced the brightness of the light so that it was more like a soft blue shadow. The juxtaposition of old (vintage style) and new (LED) was something to behold.
achinI pressed Fn+LED Mode keys together to turn on the LED. The information is given in the Layer 1 key map diagram in the little booklet that came with the keyboard. Interestingly, pressing Fn+LED On/Off keys worked only after I pressed Fn+LED Mode. The key map also shows other LED keys that you can try, to play around with the backlight. I pressed Fn+LED Pattern Next to cycle through the various light patterns and colors.