is made from 'solution dyed' polyester fibers ... meaning the dye/color is 'inside' the fiber.
Sunbrella being polyester by itself wont support mildew growth; but, mildew will grow on the 'dirt' that is attached. If you remove the 'dirt' the mildew will probably be completely removed with the dirt. A 'little bit' of chlorine bleach or specialized 'mildew cleaners' if needed to remove the 'shadows' of mildew remaining after cleaning
'probably' wont affect the color of the polyester .... test first in all the usual 'unnoticeable' areas in case the polyester is strongly UV damaged/degraded and has become 'porous' - the lighter the color the faster the UV damage. If the dodger
, etc. is still 'new' use only 'mild' detergent or mild soap to clean it.
Be careful when washing/cleaning as the repellent is a coating of the fibers and is fairly easy to remove by washing
, etc. Glen Raven Mills the Sunbrella Mfgr. recommends the use of APSEAL 303 Repellent (Restorer) .... dont confuse with Apseal 303 Protectant (for UV protection). These 'water repellent compounds' (fluorophosphates) are being rapidly removed from the USA marketplace due to some potentially 'grave' environmental concerns (includes 'Scotchguard') .. so you better 'hurry' if you need to also restore the repellent.
"Gentle" soaps and detergents (low-caustic) with 'gentle' scrubbing is what you want to do to keep the repellent intact.
Powerwashing or hard scrubbing may entirely remove what is left of the repellent coating .... so accept the potential risk of removing the repellent coating if you powerwash or aggresively 'scrub'.
You can also check out this info on the Sunbrella website.