Equipping Items Help

[neurolyte]

In my manual it says to press L while having an item selected (withing the PARTY menu) to see if it improves my character (by turning blue) or decreases my character (by turning red). Ive tried this a million times, and it will not work. I have to equip items then manually go check to see if it improves my character. its quite annoying. Not only in the PARTY menu, but what about in the SHOP. Is there any easier way to see if the item I want to purchase will improve my character BEFORE buying it? (Instead of manually checking the item i have equipped with the one i want to buy?) Can anyone help me out with this?

Thanks guys.