Human eyes have three kinds of cells (photoreceptors) for color detection. They each react to either red, green or blue light. If more than one of those cells are activated, your brain interprets the light based on what cells activated, and how strongly they activated. If red and green cells activates, the light is seen as yellow. The light is seen as white if all of them activates fully.
This also means that light bulbs can produce white light by simply producing three wavelengths (colors) of light. The problem with that kind of “fake” white is that colors will look wrong under such light due to the way how objects reflects light. This is very common with low quality LED lights, and even the best smart lights aren’t very good at it. When buying LED lights, you might want to look at the CRI (Color Rendering Index) value and make sure it’s above 90, or as high as possible.
Just buy bananas that are of the ripeness you like and put them in the fridge. They’ll easily last a week or two and tastes better too (my opinion). Don’t worry if the shell turns brown, the insides are still good. Place them in some kind of container (plastic bag will do) when you store them in fridge and they’ll probably last a month if not more (I wouldn’t know, I always eat them sooner).
When storing in fridge, the low temperature slows down ripening but oxygen causes the shell to turn brown. When the shell is brown enough it will start to ruin the insides. The plastic bag, or other airtight or near airtight container, reduces the amount of oxygen that gets to the bananas. When there’s less oxygen to turn the shell brown the bananas will last who knows how long. In room temperature the shell and the insides will ripen about at the same rate, and usually pretty fast.