Apple Park t-shirts are available in eight different colors. Green, yellow, orange, red, blue, cyan, white, and black. Only the white and black t-shirts feature a multi-color ring.
Each t-shirt cost US$43.60 (S$58). US$40 + US$3.60 (9% sales tax in Cupertino).
If you are an Apple employee, you will get 20% discount. So after discount, each t-shirt cost US$34.88 (S$46).
You can get Apple Park t-shirts from the Apple Store located inside the Apple Park Visitor Center.