Germany Uniforms
Germany's boots had metal spikes on the bottom for better traction in the trenches or muddy areas. The uniform colors were usually blue with red trim. The bright colors weren't anywhere near to being able to blend in with their surroundings. The helmets had the distinct spike on the top to show that they were the Germans.
Austria-Hungary Uniforms
The Austrian-Hungary army was known for their colorful uniforms. The jacket came in two options. The first was in wool with a standing collar. The second was a linen version (for summer) with a stand-and-fall collar. The pants came in several patterns. The Hungarian units had trousers with lace trim. Mountain troops wore knee pants with long socks.
Turkey Uniforms
This is a picture of a Turkish infantry man uniform (right) and a General staff's uniform (left). Turkish infantry uniforms are a kind of uniform that are easily distinguished from other positions because of their dark green collars.
Bulgarian Uniforms
Bulgarian's are arming machine guns while wearing gas masks. They took their ideas for the gas masks from the German's.
This is the Bulgarian infantry jacket used during WWI. The red on the shoulders and trimming the black cuffs represent that the soldier was part of the infantry.
This is the Bulgarian's helmet. The clearest distinction on it is the white, green, and red symbol.