His hair is depicted as a gradient or a mixed combination of dark to light colors. The gradients range from black or blue-black to a more vibrant, iridescent blue to a lighter teal or turquoise at the tips.
The exact amount of color needed would depend on:
* The length and thickness of your hair: Longer, thicker hair will require significantly more dye.
* Your current hair color: If your hair is already light, you'll need less dye to achieve the desired vibrancy. Darker hair requires pre-lightening, which adds another step and products to the process.
* The specific dyes you use: Different brands and types of dye have varying levels of pigmentation.
Since Inosuke's hair is a gradiant, you would need to determine your hair's length and then determine how much of each color gradient you would like to have. Depending on your decision, this would then determine how much of each color is needed.
I strongly recommend consulting with a professional hair stylist. They can assess your hair, recommend the best products and techniques, and give you a more accurate estimate of the amount of dye needed. They can also help you achieve the multi-toned look without damaging your hair.