I thought all Nintendo 3DS are the same but I was wrong. Erica Griffin who is collecting the Nintendo 3DS said the consoles came with a two different screens; an IPS or TN. IPS screen has a better color compared to the TN.
There is no way you can determine whether the screen is IPS or TN unless you already bought it. Since the Nintendo 3DS comes with a dual screen, some lucky owner got both IPS screens. The following video shows the comparison between both screens.