Relationships linking to different records with colored rectangles stored in container fields or calculation fields selectively returning different container field contents with a container result type might work for this.
Conditional formatting or "hide object when" (fileMaker 13 only) settings could also serve.
But will each field for a quarter always be either fully white (empty) or fully colored as shown in your example?
Yes, each quarter in the line will be either fully white or fully colored.
Knowing that I also use FM 13, what would be your approach? Do you by any chance have an example that I could use as guideline?
Thanks in advance for your additional input!
Finally I used a portal combined with conditional formatting and it works really perfectly!