A Blue Magic wall means you cannot walk through it. Either cause:
·they're used with an aggro PvP setting towards you. or cause its your own magic wall in regular Open PvP worlds.
·Cause of the old PvP settings from Retro Hardcore PVP worlds and Retro PvP worlds.
A yellow magic wall means you can walk through it. You can see it if someone else on green pvp mode uses it around you on Open PvP servers and Optional PvP servers. Most monsters can't walk through it, but people will still be able to do it unless you switch your pvp mode to aggressive or they do it.