Engrave your horn first! ____ Leather dye is not the best choice!..Rubs off easily after a while __ Use RIT dyes! For the spout end use a strong hot water solution of RIT in dark brown or black if you want. Mask off the area of the horn you do not want to get any dye on for the spout area. No problem if you do, as you can just carefully sand any run off with 400 grit sandpaper and #0000 steel wool. __ When ready to dye the main body of the horn, use RIT dye again in a color you like in a large enough kettle, pot or bucket big enough to hold water and the horn. __ Use a box of yellow (or two) and a pinch of orange and a wee bit of brown makes a nice old amber color, but you will have to experiment mixing different colors until you get the color your looking to use!
You can submerge the entire horn into the amber or main body color, as long as it is lighter than the darker spout tip and the spout color will not change color at all! The time you leave the horn in either color of dye will determining the deepness of your color, but usually 30 minutes should do it!
NOTE! ... Bring your RIT dye water to a rolling boil and then turn off heat before emerging your horn and be very careful!
Rick