Bash function to convert hex to 256 terminal color.

fromhex.bash

# fromhex A52A2A
# fromhex "#A52A2A"
# BLUE_VIOLET=$(fromhex "#8A2BE2")
# http://unix.stackexchange.com/a/269085/67282
function fromhex() {
  hex=$1
  if [[ $hex == "#"* ]]; then
    hex=$(echo $1 | awk '{print substr($0,2)}')
  fi
  r=$(printf '0x%0.2s' "$hex")
  g=$(printf '0x%0.2s' ${hex#??})
  b=$(printf '0x%0.2s' ${hex#????})
  echo -e `printf "%03d" "$(((r<75?0:(r-35)/40)*6*6+(g<75?0:(g-35)/40)*6+(b<75?0:(b-35)/40)+16))"`
}