Thanks very much for your help troubleshooting my issue. I think it comes from the WB setting. I remember correctly that I had a brim hat on the day I took those pictures. Also, my WB setting wasn't correct. I will have to learn how to set it from YouTube.
I was glad that it wasn't a problematic camera. I also downloaded Nikon Viewer software to adjust my pictures.
Thanks again for your help. I look forward to learn more from you guys in the future.