You may already know this, but it really helped clarify things for me when
I learned it- so here goes:

I think it's an important mental note that the color sensor does not find
blue, red & yellow. It will find "blue" and "Not blue". It will find
"yellow" and "Not yellow". etc. (although you can expand it's "search" and
include other colors near that one color you wish to locate.)    It does
this by keeping inside a range of reflected light.  When your light sensor
measured something, you were only looking for a threshold- does the light
sensor see above (or below) this *one number*? With white reflecting all
the light that is bounced off it and getting an ideal reading of 100, pitch
black absorbing all light and getting a reading closer to 0, and your mat
giving you some number in between the two, which became your threshold of
course.   With the color sensor, it asks the program; do you see (35-70)-
yes or no?  If yes, do this action; if no do this other action. It is built
to have configured ranges that are more likely to be those colors'
readings.  But the reflective quality of the material, the light in the
room and distance of the sensor from the mat all affect the reading so I
think your hope to find "true blue" is more difficult to pin down, even if
you had every bit of research on the reflective quality of a true blue
color, the FLL mats and the variation of absorbed light differences of the
color sensors.

I only have the NXT models, and we were not able to see what number our
color sensor saw and I hope that the EVO3 would fix that, but I don't
know.  The way they variegated the colors in the mats makes it super hard
for the older NXT models to find a blue color.  Nothing is truly
impossible, but it's much harder.
Good luck,
Brandy


On Tue, Oct 22, 2013 at 3:46 PM, Sonya Shaver <[log in to unmask]> wrote:

> Hi Kathy,
> When you're using the color sensor, in whatever block you're using, select
> Color Sensor - Compare - Color.  Then you can choose what color you want,
> as opposed to a reflected or ambient light intensity.  I've tried to attach
> a picture so you can see this.  There are also a lot of tutorials in the
> software that might be worth checking out.
>
> Good luck!
> Sonya
>
>
>
> On Tue, Oct 22, 2013 at 3:00 PM, Molina, Katherine <
> [log in to unmask]> wrote:
>
>>  Hello all,
>>
>> I am very new to the EV3 system. I did not use the color sensor with the
>> NXTG. Can anyone direct me to a tutorial on how to program the color
>> sensor? I'm not clear how it's different from the light sensor. It seems
>> there must be a way to tell it to "find blue" rather than a certain
>> reflected light intensity.
>>
>> Thanks so much!
>> Kathy Molina
>>
>> PS Apologies if this topic has been covered already.
>>
>>
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