Answer: your (Uds.) yellow chairs - Ustedes sillas amarillas
your (Uds.) black pens - Ustedes bolígrafos negros
Step-by-step explanation:
Ustedes is used when talking about more than one person, which is why tu is not used.
chairs=sillas
yellow=amarilla
pens=bolígrafos
black=negro
The colors have an "s" added to the end to make it plural because chairs and pens are also plural. Also, the color comes after the noun in Spanish, so it is "Ustedes bolígrafos negros" and "Ustedes sillas amarillas" instead of " Ustedes negros bolígrafos" and "Ustedes amarillas sillas".
Step-by-step explanation: