pocketmine\level\generator\biome\Biome::generateBiomeColor PHP Method

    private static function generateBiomeColor($temperature, $rainfall)
    {
        $x = (1 - $temperature) * 255;
        $z = (1 - $rainfall * $temperature) * 255;
        $c = self::interpolateColor(256, $x, $z, [0x47, 0xd0, 0x33], [0x6c, 0xb4, 0x93], [0xbf, 0xb6, 0x55], [0x80, 0xb4, 0x97]);
        return (int) ($c[0] << 16) | (int) ($c[1] << 8) | (int) $c[2];
    }