This shade of pea soup green is officially the best color for notebooks. Bonus, the super-smooth paper inside is a treat for writing, it lays nice n' flat when open, and its unique grid/lined hybrid paper makes for massive adaptability.
I use mine to make to-do lists in my bullet journal, draw cartoon balloons in my pen pal letters, or spice up notes with polka dots. Think of all the possibilities.
This is a cute palette of colors that allow you versatility with both a thinner tip and a thicker chisel tip. I use Mildliners for my bullet journal, as well as for highlighting.