Hi Paul,
Use the following expression in the conditional formatting of all check boxes.
my:field1 = string(true()) or my:field2 = string(true()) or my:field3 = string(true()) or my:field4 = string(true()) or my:field5 = string(true()) or my:field6 = string(true()) or my:field7 = string(true())
Here field1,field2,field3,.. etc. are the check box fields.
It will help you.