Hi Guarav,
There are 2 ways to create this
The First way would be to:
Make 1 green Button and 1 red Button.
In the visibilty settings check by expression if the Fields are empty
$currentObject/field1 != Empty and $currentObject/field2 != Empty
And so on ..
If all fields are filled out then the green Button will be visible.
The other way would be to:
Make 1 button.
Make a css class for color green and for color red.
In the Button Properties go to Apperance and set a dynamic class.
In this class make again the expression.
If $currentObject/field1 != Empty and $currentObject/field2 != Empty then 'green' else 'red'
Hope this Helps,