Level 839 Green Letters

jenjen88

I'm on level 839 and noticed there are letters in green but cannot figure out if there is any rule implemented. 

abe_coffee

the letters in green indicate that a tile is part of the find-the-letters word ...

sometimes a valid letter does not turn green but it appears to work most of the time ...

this is a nice feature that helps a player and can prevent playing a crown when a playable letter is already on the board