Derek if you look on the high street at the moment everyone is offereing 20% off, I read a book about discounts and psychological triggers and they say that anything less than 20% off won't work as it's not percived as enough (look at the laughable vat 2.5% discount, not enough benefit)
I would add onto your colour flier,
"a genuine 10% off"
People will see that you as an honourable company and they can trust you, less is sometimes more it all depends on how you sell it.
Shaun