Taffy,
The unit tac sign for 8 Sig Regt and 143 Sig Sqn (which is part of 8 Sig) is a red '40' on a white over blue background. Attached is a poor picture of 40, plus a similar one for 103 Sig Sqn, which will give you a better idea of what 40 should look like.
It also had a Formation tac sign for 2 Div - also attached.
Cheers.