burkphoto Loc: High Point, NC

Are you saving raw files or JPEGs? The processing of JPEGs, including the JPEG preview image stuffed into a raw file, is done in the camera. White balance errors are difficult to correct in post-production.

The processing of raw files is done on your computer as post-production. You can get any color you want, including the exact same color the camera would have generated, if you use the right software.

Color management may also be an issue. Many photo processing software programs have a "color management preferences" control panel, where you must set things such as:

Working Color Space — This is usually a wide-gamut color space (ProPhoto RGB or Adobe RGB) used by the operating system and software for internal color conversions.
Default Color Space — This is usually sRGB. The sRGB ICC profile is sometimes not embedded into sRGB images, in which case, sRGB is always ASSUMED to be the correct profile, but may not be.
Monitor Profile — If you have multiple monitors, each one must have a separate ICC profile. Set this to the one you're using to evaluate color.
Soft Proofing or Simulation Profile — This is usually your printer profile for the exact paper, ink, and printer combination you are using, OR, it is your lab's printer+paper profile.

I'm not familiar with Picassa. Check its documentation.

Checking the EXIF information for your files may give you a clue. There may be a white balance mis-match between camera setting and actual lighting conditions, OR an ICC profile mis-match.

One example that would result in a strong magenta color cast is leaving the white balance set on either "4100K" or "Fluorescent," or a Custom White Balance that was set under Cool White Fluorescent light, and subsequently photographing a daylight or flash scene. All of those settings introduce a magenta bias designed to kill the green cast of Cool White Fluorescent light.

HOWEVER, if your thumbnails look normal, I sort of doubt there's a white balance issue.

Finally, is Picassa up to date with camera profiles? If not, it shouldn't even attempt to open a D500 file, but... again, I'm not familiar with it.

If you have the software that came with your camera, install it (Nikon View NX2?), configure it for proper color management, download images, and try again...

https://www.nikonimgsupport.com/ni/NI_article?articleNo=000001049&configured=1&lang=en_US

Keldon Loc: Yukon, B.C.

Thank you everyone who has contributed to solving my problem.
As I suspected and feel pretty stupid for discovering so simple a solution, the issue lies with Picassa. It never had the D500 entered as a supported camera prior to their purchase by Google. Once I found this out and put my photos through my other programs everything seems fine.

Thanks again to all who made suggestions and gave advise. It is much appreciated.

gvarner Loc: Central Oregon Coast

Check your lens connection to the camera. I've had similar effects when the lens wasn't properly seated to the camera body.

JPL

You could and maybe should use Nikon software for editing your files. It is free and works well, in my opinion a class above Picasa and class below Lightroom. But with that you have no color issues. It is called ViewNX and you can download it from the Nikon website.

Fotoartist Loc: Detroit, Michigan

Open it in Photoshop and click on the background with the grey eyedropper in Levels.
This will remove the magenta cast. Won't help with what caused it however.

cjc2 Loc: Hellertown PA

About 18 months ago I abandoned Nikon software for Lr CC as the Nikon stuff was too far behind the curve and had too many bugs, at least for me. The result was a better, higher quality, faster and more efficient post process. I'm happy as a clam, and wouldn't consider turning back. What I did loose in the process was having Nikon software doing the conversion on the Nikon raw files, and that is exactly the issue which delayed me in making this change. Although there are differences in ACR's interpretation of Nikon Raw files, it is no additional burden to get them to where I want them and that whole process is now much faster as well. I stoot 99.9% RAW, so some level of post is to be expected. The better I capture the image, the less work needed in post. I shoot with the D500, D5 and D810. Best of luck.

jerryc41 Loc: Catskill Mts of NY

Good to know.

burkphoto Loc: High Point, NC

That figures. Picassa is "abandonware".

If you need a really good, inexpensive solution besides your camera manufacturer's software, look at Affinity Photo from Serif. The latest version runs on Macs and Windows, costs about $50, and gets rave reviews. It was Apple's Software of the Year a while back.

https://affinity.serif.com/en-us/photo/ (or in the Apple App Store if you are a Mac user)

stillducky

Picassa can't handle your d500 raw. Can you update it? Test the d500 by shooting and checking out a jpg instead of raw

stillducky

danoliver Loc: South Central Kentucky

JIM Bobby, u the closeth thing we got to a true idiot !

rehess Loc: South Bend, Indiana, USA

I hadn't seen that term before, but I really like it!! It quickly summarizes Picassa's non-status.

burkphoto Loc: High Point, NC

Any software that is finished is abandoned soon after. When all the bugs are swatted in the last release, it is time to release the next version!

There's some advice in there somewhere.

Fotoartist Loc: Detroit, Michigan

Here's my advice. Keep a legacy computer system that you can go to if a favorite program works for you on it but has been abandoned. Everyone has an old but still good computer. I have mine connected with a server. I have some programs that are over 20 years old that I use on it and then transfer the output to my current desktop. You can streamline the older computer by stripping it of most everything but what you need to run your favorite programs.

burkphoto Loc: High Point, NC

That is what I do. PowerMac G4 with OS 9 and PageMaker 6.5!