@VENU K V
Looks like the artist is using ink as a paint. You can get either waterproof or watersoluble inks. It's best to get waterproof ones as they are pigmented and hence lightfast. The ones I recommend are Sailor KiwaGuro, SketchINK, De Atramentis Document.
From what I see, he/she applied the ink, let it dry, and applied colour later.
@VENU K V
Looks like the artist is using ink as a paint. You can get either waterproof or watersoluble inks. It's best to get waterproof ones as they are pigmented and hence lightfast. The ones I recommend are Sailor KiwaGuro, SketchINK, De Atramentis Document.
From what I see, he/she applied the ink, let it dry, and applied colour later.