Q:

How to send ether to a cold storage account? 

Is it possible to do the following:

Back up the keystore on a usb drive. 
Format the computer used to generate the keystore. 
Send ether to a public address in the keystore. 
Reinstall geth (or other ethereum cli), import the keys and have the updated balance? 

Thanks

A:

Yes it is.  
Basic Formula:

Install an Ethereum client to a computer that is freshly formatted (preferable), or at least one that is disconnected from the Internet. 
Generate your key(s) using an Ethereum client. 
Copy the Ethereum address generated and send 1 Ether to that address using another computer/device. 
Check an Ethereum blockchain explorer to make sure your 1 Eth you sent arrived. 
Now that you have confirmed your test transaction sent, send any other Ether you want to that address. 
Put the offline-generated keys on a USB stick or print our the public/private key using an Ethereum paper wallet generator (the paper wallet code for the generator should be examined for malware and used on the Internet disconnected machine)
Whenever you need to send a transaction from your offline-generated key, create/sign the transaction using the offline computer and transfer that raw transaction data to an online computer to proceed with the transaction. 

Here is a guide to do the above using the ethkey tool from the Ethereum C++ client team.