Bleu nuit is darker and can read black more easily - it's a dark navy. Bleu encre is brighter (although not super bright) with more purple - it is indeed inky. I'll try to take a photo but I have Clemence and chèvre and so the colors look VERY different - it's also so much about the leather you choose.
I will grab my mom’s bleu encre clemence pico to comparenwoth my bleu nuit Evelyne tpm tomorrow for a side by side picture. My mom is asleep and I can’t sneak into her room right now. Here’s a photo of each of them separately.