I hold no particular definition of the shirt color either. Some denominational roles dictate specific shirt colors to respective duties or offices. I have never explicitly worn any particular color except to complement the color scheme of a wedding ceremony or a grey-shade shirt I reserve primarily for funerals.
I'm not obsessive, however, about wearing my white collar. You will usually only see me dressed in this fashion for formal occasions or in times when I am needed to be distinctly visible in my role. We won't get into the speech I make when someone tries to call me Father. (maybe in another article sometime, I keep a sign on my desk explaining my scripturally based displeasure with that title) I believe visibility is crucial in ministry, especially when working with groups of people. We operate a community-based ministry without a church building. Being such makes my visibility even more critical; I have T-Shirts that identify me brightly too. Not everyone around you will have direct knowledge of who you are or the role you perform all the time. However, everyone knows you in those more intimate settings, "lay attire" is acceptable because you are known or informally introduced.
I visit other churches occasionally on Sunday mornings when my ministry duties allow. During those times, I dress to meet the culture of that church. I would not dare set myself apart intentionally from the pastor of that church unless such a formal occasion made it reasonable. I believe being a visitor and standing out as a spiritual leader unannounced would be disrespectful.
I see my use of this dress style as crucial as that of a uniformed police officer, firefighter, physician, or other civil officials in our communities. It is not a matter of cocky selfish pride or a statement of egocentric importance. Instead, it is about visualizing the office's identity to those who need to seek the service or recognize me as a clergy member. I have never had trouble visiting a hospital patient wearing my clergy attire with proper identification. However, I have had difficulties in casual or business dress even with my ministry identification, for example, sake.
When I dress up in this fashion, I do it with the same respect as a United States Marine, for example, has for their uniform. I didn't earn the right to wear it; I have the honor of wearing it, and I wear it in humble respect, honoring my Lord and Savior as his ambassador. It's that simple.