Navigo Pass

It does not have to be that fancy. For mine, I took a selfie on a plane background, then printed it at a reduction that got it to the right dimensions. Cut it out, and Voila! ready to go.

I just photocopied an existing photo of myself, cut it to the correct size and brought it with me.
I believe it was colour.

There are 2 different Navigo Passes and only 1 needs a photo. The Navigo Easy (NE) doesn’t require a photo, you can use this pass to load single tickets, a carnet of single tickets etc on.
The Navigo Decouverte (ND) does require a photo, you need this card if you want to buy a week or month pass for instance.

So, first of all you need to make sure you actually need a photo. What pass or ticket do you wish to load on a Navigo card?
Also have you thought about using your phone or smartwatch to buy tickets or passes? You can very easily set up a digital Navigo on your phone or watch.
See details here; https://www.iledefrance-mobilites.fr/en/tickets-fares

There are 2 different Navigo Passes

There are a lot of different passes: day, weekly, calendar month.

There are a lot of different Navigo cards, but for tourists the Easy and Découverte are the most important.

There are cards, tickets (single use), and passes ( unlimited use within purchase period and coverage). If you mix up the nomenclature, it makes explaining and understanding public transportation more confusing than it need be.

The photo for the Navigo Découverte must be 25 x 30mm, an original photo, not copied, not scanned. There is no requirement that it be in color. If you decide to manipulate an existing photo, make sure that it is a very good likeness. If a controller does not think that your photo meets the requirements, you can be fined 50€ (and I know people who have been fined).

I have made maybe a dozen cards; two each for my husband and myself over the past 16 years and cards for family. For the first cards, I cut head shots out of snapshots. For the last ones I printed pictures in color on regular paper on my computer printer. As noted they should be 25/30mm and a straight on head shot that is clearly recognizable. When you get controlled, the agent will look at the picture, compare it to you and then check that it has been validated. It can be color or black and white but needs to be clear and look like you. Once the card is assembled it is under a clear plastic flap so the quality of the paper is not important but the quality of the image is.

To add, for anyone lurking - the N Decouvert Card is good for 10 years, so it's well worth the 5 Euros if you're returning to Paris.