Many people find it very difficult seeing the letters on a standard computer keyboard (which tend to be small and grey on a beige background).
There are a number of large, hi-contrast, sets of keyboard stickers available at little cost , for example see Fig 1. Simply stick them on the keys of a standard keyboard and it may be much easier to find the key you are looking for.
Fig 1 - Hi-visibility keyboard stickers
The above example shows white letters on a black background (often found the easiest colour combination to see), but they are also available in black on white, black on yellow and yellow on black.