OK I'll link the danish test, this test is done with 2 cars that are identical, except for the color of the paint:

https://livsstil.tv2.dk/2018-05-24-bliver-en-sort-bil-varmere-i-solen-end-en-hvid-tv-2-har-lavet-testen

Konklusionen er altså, at den sorte bil ikke varmes mærkbart mere op end den hvide.

Translation:
The conclusion is that the black car does not heat up noticeably more in the sun than the white.

So it does a little bit that you can measure, but not enough to really make a difference.

Det skyldes ifølge Christian Bahl, seniorforsker hos DTU Energi, at bilerne opvarmes gennem ruderne.

According to Christian Bahl senior researcher at DTU energy, that is because the cars are heated through the windows.
(DTU is a well recognized institution for scientific research in Denmark.)

This is the t-shirt one I remember.

From

https://mainichi.jp/english/articles/20230726/p2a/00m/0sc/014000c

Sorry can't find it, all I can find in english are some where the data isn't clear.
If a white car has brighter interior it will stay slightly cooler, I cannot find a test where everything is the same except the color of the car.
What I can say however, is that the test I saw was performed in Denmark. It's possible countries with hotter climates may observe some difference?

Obviously the main source of heat is what enters through the windows, and how much is reflected out again does have an influence.,

If a white car has white seats and interior, they will obviously not heat as much as black seats and interior.

The white color on the exterior will also reflect more light into the car, except maybe at noon.

Edit PS:
I linked the danish test in a new response.