Define preset colors using FastLed library
Your colors array should be CRGB type, not char *.

CRGB colors[] = {0x000000,0xFFFFFF,0xFF0000,0x008000,0x0000FF}; // black, white,r,g,b


For your second problem - you are overflowing the bounds of your LEDs array:

for (int i = 0; i &lt;= NUM_LEDS; i++) {
  leds[i] = 0xFF0000;//colors[col_indx];


You are going from 0 to 10 inclusive. That's 11 iterations. There is no such array slice as leds[10], so the value you write to it ends up overwriting the next two bytes in memory - and those happen to be occupied by the variable t.