The costume and weapon identify this soldier as one of the Landsknecht; Swiss and German soldiers for hire. Landsknechts were the first modern warriors trained to move as one unit. The long lances they carried could easily knock a knight in armor from his horse. Over 100 Landsknechts could cross a battlefield on foot in organized formation, directed by the signals of a standard bearer like the man in this portrait.
The standard bearer signaled the troops with the enormous orange flag draped around him in the painting. With the orange flag and colorful costume, he could be easily seen across an entire battlefield. Much of the color of the standard bearer's costume comes from the slashes in the jacket and legs, lined with fabric of different colors. It's clear why the artist included the whole figure in this portrait. Who would want to miss any details of this bright and flashy costume?