Flutter: Change Checked Colour of Checkboxes

I am trying to create a bottom sheet with checkboxes. I'm finding it difficult to get the checkboxes to be checked and show a different colour once tapped. At the moment the checkbox just stays empty.

How would I solve this?

bool isChecked = false;

...

Column(
                children: <Widget>[
                  Padding(
                    padding: const EdgeInsets.fromLTRB(50, 10, 10, 10),
                    child: Row(
                      children: <Widget>[
                        Expanded(child: Text('Classes Booked')),
                        Checkbox(
                          checkColor: isChecked
                              ? Colors.grey
                              : Theme.of(context).colorScheme.aqua,
                          value: isChecked,
                          onChanged: (bool value) {
                            setState(() {
                              value = true;
                            });
                          },
                        ),