2 of 4 added 244 characters in body

If you haven't GNU grep available, here is something more portable:

grepc()
{
  pattern=$1
  shift
  sed 's"'"$pattern"'"^[[32m&^[[0m"g' "$@"
}

You can customize the color using one of these codes

30  black
31  red
32  green
33  yellow
34  blue
35  magenta
36  cyan
37  white

Using 7 instead of a color code will put the string in reverse video.