Somewhat of an unsung hero in the arsenal of tools included with OS X
is the DigitalColor Meter which allows you to precisely determine the color
specifications of any image displayed on the Macintosh screen.
In the following example, I used the DigitalColor Meter to determine the exact color of the nose of the rag doll to obtain the RGB (red, green, and blue) color levels. I point the pointer to the exact area that I want the color meter to measure as exemplified in the example.
The DigitalColor Meter panel contains a large square which shows the area
being considered, the center of that area being marked by the cursor and a small
square which shows the color obtained by averaging the colors shown in the large
square. The large square can be set to cover an area of varying number of pixels
and this can help to determine an appropriate color to represent an area which
is multi-colored. If you look closely at the screenshot you can see that there is
a variance, albeit subtle, in the included colors.
DigitalColor Meter gives the user the option of choosing from a number of
commonly used color specifications including the ubiquitous RGB and CMYK.
Once you becomes a user of Digital Color Meter you will truly wonder how you got along without it. Especially if you make your own gift cards, brochures, web pages, newsletters, etc. and are a stickler for matching things perfectly.
Oh yeah, you will find it in the Applications folder. Choose Utilities > Digital Color Meter. If you are running OS X you will have it. I keep it on my Dock because it use it frequently.