whipstickgostop - it appears you need CEP or if you have installed CEP then you have disabled custom content (this is a thing that startes with Nightlife expansion pack and later expansion packs)
install CEP from here:
http://cep.modthesims2.com/and when your game starts, watch fpr a pop-up warning that has the option to disable and enable custom content, choose "enable" and go to the game - go into a neighbourhood, then exit the game.
Now start the game again and then leave the custom content "enabled", go into play as per normal, and the flashing blue should stop.
If you see flashing blue accessories like jewellery and glasses, you need to have your sim go to a mirror and "change appearance" - no need to do anything fancy here just change one thing and the game should correct a flashing blue item worn by the sim.