The code on the sole: FG (firm ground) for real grass, AG (artificial ground) for turf, flat rubber for indoors. The surface decides which boot you wear, not the colourway.
The sole is your only connection to the ground — on every acceleration, every stop, every change of direction. FG boots carry longer, firmer studs for real grass; AG boots use shorter, more densely spaced studs for artificial turf. The wrong boot on the wrong surface means noticeably less grip, and less grip means slipping at exactly the moment you accelerate. Indoors and in futsal you want a flat, non-marking rubber sole underneath: studs raise the risk of falling on a hard court. Two things get overlooked again and again. First the fit — snug, but never painful. Second the wear: worn-down soles slip even when the upper still looks fine, so turn the boot over before the season starts. In beach soccer the question settles itself: boots are banned, only elastic foot bandages are allowed.