> Slow enough for the human eye to detect. 2 Hz or around there.
> 
> The application is a brute-force method for figuring out 
> which COM port the device is sitting on (in case the baud 
> rate is set wrong). RTS driven by software toggles the red 
> LED on/off, resulting in the rapidly changing yellow/green.
> 
> BTW, I just realized that there is a mistake in my original 
> post. Although there is another condition where the light 
> changes from red to yellow, in this particular case, it's 
> changing from yellow to green.
> 
> My hope is that the brightness changes enough (2 LEDs on vs 
> just one) to where the difference can be detected by color 
> blind people.

I am color blinded. I barely can say wich of the tree on-states of a R-G
led is on. I see the off state clearly...   :o)

In my case, I do not perceive sensible differences in the R-G led colors,
but in its light intensity, as you say; so, in my case, the ability to see
your patterns depends greatly in the light intensity in the room where the
equipment is. I often have to use different approaches to see differences
in color: turn the lights off, put a hand over the led making a "tube" and
look through it ...or opening the product, make a little rework and fit two
leds instead of a bicolor one.

You could use a bicolor led that uses blue instead of green or red; this is
much more clear for me. Or, you can use two leds of ANY color placed
side-by-side, so the color problem turns to a position problem. Much more
easy to tell (for me).

Thanks for worrying about color-blinded people. A word of caution here, for
all of you not color-blinded: there are A LOT OF people out there (mainly
men) with problems to differentiate colors. I often use criterions based in
my color limitations when I buy things. At times, the fact that I can use
the product without the need of turning off the lights is the key factor
that makes the decission between similar products. Not the price, not even
the specifications, so this is a key factor in my designs. And this is
specially true in our (electronic thingies full of color lights all around)
world.

Regards,

Alvaro Deibe Diaz.

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