Why every time open the model, the defined color will be removed and turn back to default? Can fixed the color setting?
Which color specifically? Which STAAD.Pro version are you using?
STAAD.Pro CONNECT Edition V22 Update 10
To the best of my knowledge, this is how the program is designed. If you color the beams by property, specification or group, the program will use that coloring for the active STAAD session only. However, once you reopen the model, the colors will be set to the default beam colors.