Bottom Navigation Bar manages the index with Provider, and the code of Bottom Navigation Bar is written as below.
I have a total of 5 icons and I just click on the second icon, but the color changes and it doesn't change after that.

@override
Widget build(BuildContext context) {
  return Expanded(
    child: InkWell(
      onTap: onTap,
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          isSelected
              ? CustomGradientIcon(
            icon: icon,
            gradient: gradient,
            fill: 1,
          )
              : Icon(
            icon,
            color: FalletterColor.gray700,
            fill: 1,
          ),
          const SizedBox(height: 4),
          isSelected
              ? ShaderMask(
            shaderCallback: (bounds) =>
                gradient.createShader(bounds),
            child: Text(
              label,
              style: FalletterTextStyle.body3.copyWith(
                color: Colors.white,
              ),
            ),
          )
              : Text(
            label,
            style: FalletterTextStyle.body3.copyWith(
              color: FalletterColor.gray700,
            ),
          ),
        ],
      ),
    ),
  );
}