Somewhere along the line I ran across a standards document that did suggest different colors for different type of functions. I found this to suitable for very basic applications but in more complicated applications the color coding does not quite cut it. An example would be a system where you are integrating a half dozen type of devices. Using the same background color for all of the I/O icons will quickly render your hiarchy window rather useless!
The next issue with the color schem to represent functionality you run into is the higher level VI that do a little of this and a little of that. The standard then suggests using border colors to represent functionality. This becomes a problem in one of two ways. On large screens (like those typically used by LV developers) the adjacent colors of a border are percieved as a mixute of the two border colors. The fix to this would be to use wider borders. This inevitably lead to all of the high level VI all looking like they were dveloped by someone on LSD who was into the time tunnel effect!
I will generally encourage developers to take the time to put together a meaningful icon. LV will let you drop cut and pated BMP's into the icon editor. IF there is an logo or a picture of an instrument avaliable somewhere, I grab it and use it fot the icon. This approach makes it possilbe for other developers to take a quick look at teh hiarchy and be able to narrow things down quick to the sub-VI associated with that image.
I also encorage tehm to get used to composing their own icons. The icon editor may not be slickest tool in the world but the icons on the diagram end up being small enough that you do not need to be an artist to get the idea across. Durring my last project I wanted to use a scroll icon for all log related functions. I was curious if I could put one together fast. Start to finish to took less than three minutes. Three minutes of effort is well worth it when your are looking at a hiarchy with 500+ VI's!
Too illustrate let me relate an experience. My wife (a non-wireworker) looked at a icon I just dropped on my diagram that had a crude cartoon face with the word "NEW" above it. She said "New User?". I flet I had accomplished my task.
Encouraging art in LV,
Ben