6yo. mild diarrhea, bluish/green poop, mild tummy pain normal appetite ?

Not unusual: Child may well have a gastroenteritis. If the child is given a slow but progressive diet things should settle in two to four days. This sounds mild but must keep the child hydrated. The color thing is not unusual. Best wishes. Call the doc if not better in a couple of days.

Mild diarrhea: Could try Florastor OTC probiotics and see the pediatrician tomorrow unless worsening. Also may try apples, rice, bananas, toast and avoid milk products tonight to slow down the diarrhea. Make sure your child is taking in adequate fluids. If the pain worsens, please call your pediatrician on call.

Food?: Did she happen by chance to eat something that was bluish/green in color?? Sometimes our bowel movements or diarrhea can be the same color as what we ate or what is making us sick in the first place. Or it could just be the nature of the virus or bacteria she caught that's causing the diarrhea. If she's eating normally and taking fluids well, I wouldn't worry too much. Just keep her hydrated well.