How do I Apply a Particular Format to cells using the IFBLANK function?

I have an excel summary tab that copies information from other tabs referencing the cost of a product (guide price and actual price).

I've set a function on the summary tab, so that if the "actual price" cell (located on the pricing tab) is filled then this is carried over to the summary tab. If it's not, then it uses the guide price (from the pricing tab).

CODE on SUMMARY PAGE

=SUM(IF(ISBLANK('Pricing '!S14), 'Pricing '!O14, 'Pricing  '!S14))

This is roughly how the data looks on the summary tab. Some of these prices are from the "guide price" cells, and some have been overwritten by the "actual price cells" being populated. However there's no way to tell at the moment which are being used as there's no formatting.

I need to add some sort of formatting (preferably the guide to be grey and the actual to be green and bold) to the summary page prices, so it's clear whether the guide price or the actual price is being pulled from the pricing page.

Hoping someone can help me here!

ThanksRoxanne