Is there a way to change the msn messsenger tray icon if your using polygamy so can tell your accounts appart?

I don't think thats possible, because all polygamy does is startup MSN Messenger twice (this is same MSN Messenger as on account 1, so if you change the icon both will change).

pooooo that is to bad

It may be possible if you can find the process IDs of the Messengers, then record which PID belongs to which account. Then, you can set the icons per account.

However, this will be a LOT of work for very little effect...

EDIT: Thought of a slightly easier way...
A loader has to change the program in memory yes? So why not change the trayicon resources in memory too?

Quick how to:
1) Install one version of MSN Messenger.
2) Patch it with polygamy...
3) Rename the directory to whatever you want (eg. MSN MessengerZ)
4) Install the other version of MSN Messenger.
5) Patch it with polygamy...
6) Modify it's icons/Install a cool skin...

Now when you run one version of MSN Messenger, it won't be "skinned". But when you run the other, it will. Therefore, you can easily tell the difference between each client, provided you have "skinned" each client differently.

Note: If you are doing this with MSN Messenger 7, install MSN Messenger 6.x first and then MSN Messenger 7.

Also, note: You do not have to install a different version of MSN Messenger. It can be the same version, provided you have installed them into different directories (which should be fine, as if you used the method I outlined above, each version of MSN Messenger will have been installed into a different directory, its own directory.