It's not surprising as a color consultant to have run-ins with a color 'changing' under different lighting or in different rooms. It is our expertise that helps clients find that perfect color in an otherwise troubling room. It is always interesting when the color change/result is more drastic in a particular case compared to more subtle differences.
The three lighting sources that can 'change' a color are natural/direct sunlight, indirect sunlight and artificial light. Artificial light adds another level depending if the bulb is halogen (most like, but not the same as, daylight), fluorescent (shows more cool tones), or incandescent (shows more warm tones).
That's why you may pull some paint chips from the paint store just to feel like you are back at square one in finding the perfect color once you get the paint chips home. Retail/commercial buildings usually have fluorescent lighting, where as your home most likely does not. Your friend's or neighbor's house may face the same direction as yours, but each room is different. A blue that looks great in the store looks baby blue at home. A tan in your friend's great room pulls more yellow or orange than you planned.
I recently helped a client find a new color for a master bathroom. It is located on the same side of the house as the dining room, but has a single window compared to a door wall and is on the second floor compared to the main floor. She is keeping the existing earthy brown/terracotta tiles and wants a lighter earthy feel, but not peach or brown. In the dining room we reviewed a few color chips she had pulled. Knowing we had to look at the colors in the actual space I added some color chips to our assortment.
When we moved the color chips into the master bathroom, metamerism went to town taking neutral tans that can look yellow vs. peach and turned them muddy looking. We switched gears and found colors that looked carmel (in the dining room) held their own and didn't turn muddy in the actual room's lighting. It was a good challenge to show my client why the color would need some depth, some umph, to not crumble or disappear next to her tile, and more so why we had to look at the colors in the space to be painted, not solely in a room with better seating :)
So now you know the name of the trouble causing, although natural occurring, circumstance. If you get really stuck and need help finding the color to ~make your space personal~ contact me for a color consultation.