There actually is a test for the blue egg gene:
https://iqbirdtesting.com/blueegg
If the pullet has the blue egg gene, she will lay some shade of blue, green, or olive. If she does not have the blue egg gene, she will lay some shade of brown.
I would only bother with the test if it was very important to me, but I can't say how important it is to OP to get a bird with the blue egg gene.
If one parent is actually a Penedesenca, then she should lay fairly dark eggs (olive or brown, depending on whether she has the blue egg gene or not.)
If someone crossed two F1 Olive Eggers to produce her, so neither of her parents is a pure breed, then her egg color could be anywhere from light (blue or cream) to dark (olive or chocolate) or something in between.