Windows GUI Button sensitive color gets stuck at light-blue,

When a button is clicked with a mouse, ( or even mouse-over ) in W10 GUI client, 11.6.4, it turns light-blue.  Normally, then when the button is no longer pressed, it turns back to grey. 

Our problem is when we have an Add button, for instance, the user presses the add button to add a record, so we set sensitive = false, so that the add button cannot be pressed while the users is entering data, until the record is saved. Then, we set the add button to sensitive = true again. The Add button remains blue, but it should go back to gray.

Here is a code sample:

DEFINE BUTTON Btn-A
LABEL "&A Btn"
SIZE 15 BY 1.14.

DEFINE BUTTON Btn-B
LABEL "&B Btn"
SIZE 15 BY 1.14.

DEFINE FRAME DEFAULT-FRAME
Btn-B AT ROW 2 COL 10
Btn-A AT ROW 2 COL 30
WITH 1 DOWN.

view frame default-frame.

Btn-A:SENSITIVE = true.
Btn-B:SENSITIVE = true.

on choose of Btn-A
do:
Btn-A:sensitive = false.
/* pause 2 no-message.*/
Btn-A:SENSITIVE = true.
end.

on choose of Btn-b
do:

end.

wait-for close of this-procedure.

Why does setting the sensitive to false and back to true again make the button keep the blue colour ? 

How can we prevent this and make the button turn grey again ?  ( like button B )

Thanks in advance.