This Colorful Investigation can teach or reinforce multiple concepts at the same time, such as lab safety, chemical safety, team work, following directions, making careful measurements, identifying basic lab ware, and working with lab tools and equipment.
There is flexibility in how you use it, but I typically give little to no instruction and observe what my students do. Because this is not a "dangerous" lab (with the exception of food coloring), I am quickly able to see if my students know and understand what lab safety gear should be worn, if they can work cooperatively as a group, if they know to ask for help when they aren't sure what to do, if they can use basic tools and measure accurately with them, if they know how to clean up at the end of a lab, etc...
Grading the lab (if you choose to) is fairly easy. Just a quick visual check of the group's final test tubes is all it takes!
One of the most crucial parts of this lab is the discussion you have afterwards. What are your expectations during a lab and why are those rules and expectations in place? Why do we wear the safety gear? Why should group members have specific jobs/roles? Why is careful measuring important? Why do you need to know the names of lab equipment?
This lab and the discussion you have following will be memorable and provide a foundation for all of the investigations the rest of the year. Keep referring to it!