how to make groups of neopixel leds

Other Hardware LEDs and Multiplexing
4

So and with this code, only the S wil be red?

No.
This is because the setPixelColor methods expects a single number defining a single LED, what you are passing it is an array address.

So have a read of reply #1 again. The array bit is fine but how you drive it is not.

EDIT - as the strips always have consecutive numbers, just store the first and last LED number in the array. Remember the first LED’s number is zero.