Colored background on pokestop items? [duplicate]
Solution 1:
Ok after some searching I've found this out:
Yellow items are bonus items given for your first Pokestop of the day.
Yellow items are also given at Gyms if you have a Gym badge
Blue/Red/Presumably yellow for Instinct? items are given at Gyms when you spin a disc on a Gym that your team
In your example the Pokestop must have been your first of the day, hence yellow items. The other two are gyms controlled by your team, both of which you have a gym badge for, so you got yellow and blue items.
This guy seems to confirm this.
Niantic confirm the Gym aspect.