Coolant recommendation

[Tailwind]

Guys
My Cousin has a '03 S, and the coolant tank is just above the low coolant warning level.
He has yellow coolant and wants to replenish the overflow tank and not have to do a complete flush. He is aware of the danger of mixing coolants. I had green in my '99 when the tank split and after research used Peak Pink premixed to top up.
I see Dex-Cool is recommended for his car, as is Peak Pink.
Please give me your opinions.

TIA