RGB values for CMYK color varies. Best choice? (Using CS3)

I open the ai File in Photoshop (File > Open) and don't change the settings in the dialog. File pops up and I hit the colored area (one clean area) with the Eye Dropper. Result: Correct CMYK values:

CMYK 0/90/100/10
RGB 182/54/31
Hex b6 36 1f

Then I close the Color Picker Dialog and use the Eye Dropper on another area to change the Foreground Color. Next I hit the Color Picker by double clicking on the Foreground Color Swatch. I enter the CMYK values (same as above) and get slightly different Hex and RGB:

CMYK 0/90/100/10
RGB 182/53/31
Hex b6 35 1f

Related to this, Pantone's Color Bridge (Coated/Uncoated) fan-out swatches include Pantone/CMYK ink comparisons plus RGB and HTML (hex) values. But they are listed in Pantone color number sequence.

Neil

P, with such small differences I suppose it may be rounding errors, but I have to admit I’m also baffled.
By the way: FOGRA27 is obsolete as far as I know, FOGRA39 is the current standard (»ISO Coated v2 (ECI)« is available at www.eci.org/doku.php?id=en:downloads).

Besides that, the RGB value will depend on what RGB space you are using. If you want to give the client RGB values, you will also have to specify for which RGB colour space they apply and they will have to work in that colour space.

True that; if the intended medium is the internet it may be advisable to change the RGB-Working Space to sRGB.
The Intent in the Color Settings also influences the result.

Ok so let's say I chose sRGB and still get two values, which one should I give the client?

We're living in the stone age over here and Xerox is the ruthless profile hating ruler over the primitive 4C-worshipping, LAB-fearing barbarians.

Which colour engine are you using in your colour settings? Make sure it's Adobe (ACE). If you still get the problem, I would guess there is a bit of a rounding error because the imported graphic is not giving the exact same value out of the 256 possible in an 8-bit channel. Meaning, if you were to pull a gradient from 0 to 100% in a CMYK document, there are 256 possible values for the 100 percentage steps of each channel. Some steps get 2 or 3 values assigned to them as those 256 steps are distributed amongst the 100 percentage values. If your RGB value shows a discrepancy of one value, it's off just a fraction of a percent for the CMYK value, so in most cases you shouldn't worry about it. Just pick one.