The first Italian horns predate Christianity and were made of red coral. In keeping with the origins of the horn, consider tattooing it in either solid red or in shades of red to add dimension and texture. Either way, your artist should line the tattoo in red ink and not black. When the horns were first created, they were also a sign of fertility, so a red horn would be especially appropriate for a mother, either expecting or established.
The Italian horn is often used as a shape in modern-day jewelry, crafted from solid gold or encrusted with diamonds. To simulate a golden horn, have your artist line the tattoo with gold and yellow inks with subtle white highlights to imitate its sparkle. Determine beforehand whether you want the tattoo to lay flat on your skin or appear dimensional so the artist will know to either fill it in completely or shade it.
A diamond horn tattoo would be another image simulating an expensive piece of jewelry. You can choose to have the tattoo done in shades of silver and gray with small diamonds encrusted throughout the horn, or have the entire horn appear to be one solid diamond cut to the appropriate shape. Have the artist use light blue, yellow and even some subtle red highlights to imitate the sparkle of a diamond in the sunlight.
In keeping with the theme of an Italian horn symbolizing a unified Italian people, consider filling in the tattoo with the colors of the Italian flag. The color horn should be divided into three color sections: green, white and red. Your artist should use black ink to line the image, but make all shading and coloring with those three colors of the Italian flag. This design is most significant for an Italian person or someone with at least some Italian lineage.