If you are thinking that perhaps your walnut grips should look different in coloration have no concern there are many species of walnut leading to a full spectrum of light to dark brown depending on the species and where the wood was cut from the log. As a woodworker in my 20's I was fortunate to have worked on many projects that used (American Black Walnut) so it is what my eye was trained to expect. I always thought that S&W grips were made from the lighter color and density English walnut but that question has always come back to bother me. If someone knows of the specific species the lighter color grips come from please chime in.
Here are a pair of "K" frame American Black Walnut by Ajax I recently purchased from another Forum member because they took me back to the day. The link is to what I thought and now question what your actual grips are made from as most other S&W's stocks.
English Walnut | The Wood Database - Lumber Identification ...
English Walnut | The Wood Database - Lumber Identification (Hardwood)