What is the correct direction for hot on a vertical single handle faucet?

I'm having a hard time finding an answer to this question. On a traditional single handle faucet, one with the handle on top (such as this Delta Foundations faucet) turning to the left is hot and turning to the right is cold.

I now have two single handle faucets where the handle is mounted vertically on the right side of the faucet. In other words the lever moves forward and back to change hot/cold. The question is which direction should be hot? In my kitchen I have a Kohler Artifacts which has back towards the wall as hot and forwards towards the sink as cold. In my bathroom I have a Delta Broadmoor faucet which is the opposite; down towards the sink is hot and up towards the wall is cold. Neither has any indicator which should be which.

Is there a standard for this? It seems like both should move in the same direction for hot, either back towards the wall or forwards towards the sink. The question is which is correct? Is one installed improperly or does it just vary by manufacturer?