i trained in that gym several times.
for the Olympic-Bar (50 mm, yellow is 15 kg, red 25 kg, blue 20 kg)
for the standard 30 mm bar (as seen on this smith-press, the 15 kg´s are green)
so it´s simply different equipment (50 mm + 30 mm)
The green 15 kg´s where made from "Schnell" (Germany/Peutenhausen)