Hello Whitechild
Illustrator is a bit different to Photoshop when it comes to colour space. Where as Photoshop can only be either CMYK or RGB (or Lab for that matter), it is possible for an Illustrator document that is set up as CMYK to contain objects that are coloured RGB and vice versa. Colour profiles could conflict if there are placed objects in the Illustrator file such as Photoshop .psd, .tif, .eps files.
It's probably best to start by turning colour management off in Illustrator -- Edit > Colour Settings > Emulate Illustrator 6.0.
If you have any placed images in the document (you can verify this in the Links palette, Window > Links, if it's empty you have no placed objects) make sure they are in the same colour space as the Illustrator document (check by going File > Document Colour Mode > CMYK [or RGB]).
Next thing I would do is check your swatches palette (Window > Swatches, if it's not already open) and using the little triangle at the top right of it, hit 'Select Unused'. You can then use the waste basket at the bottom of the palette to delete any swatches that aren't included in the job. With the remaining swatches there is a square to the right of each colour listed, this square can be made of four triangles for CMYK and three verticals for RGB. Also, if there's a dot to the left of this square it means the swatch is a spot colour. By clicking on the swatch names you'll open up another window that will allow you to change a CMYK colour to RGB, etc., and a spot colour to process. (Once you're there it should be self explanatory.)
There the easy bits and hopefully that'll solve your problem. As you mention, when objects are grouped it's often difficult to see how the individual paths and shapes are coloured. To complicate this Illustrator has two other ways of grouping objects in addition to Group. These are Object > Compound Path and Object > Clipping Mask. There is a slight quirk that sometimes occurs with Illustrator where Illustrator tells you an object is coloured differently to what your eyes are telling you. I don't know if you've experienced this yet but in these instances your best friend is the Appearance palette. I'll let you explore this as and when you need to but basically it lists what Fill and Stroke colours are used within objects and allows you to clear them if necessary.
Sorry this is long-winded but hope it helps you out a bit with your current file.
All the best.
Mark