The yellowish color on your white blinds develops when the PVC component inside the plastic is exposed to ultra-violet radiation from the sun. Over time, the sun's rays break down the PVC, resulting in fragile and discolored blinds. Cleaning the dingy blinds requires using products that won't harm the delicate plastic but will restore the original look of your blinds as much as possible.
Wipe dust and dirt from the plastic blinds with a rag. Close the blinds for easier wiping, and place one hand behind them to hold them steady. Start from the top and work your way down, sliding the rag back and forth.
Fill a gallon-sized bucket with warm water and 2 tsp. mild dish soap. Wet a sponge with the soapy mixture. Wipe each blind separately, starting from the top, removing any stains or leftover dirt.
Dispose of the soapy water and rinse the soap suds from the sponge. Fill the bucket with clean water. Add 1 cup of bleach to the water.
Wet the sponge with the bleach water and wipe it along each blind. The bleach kills any mold or mildew and may reduce the yellowed appearance of the plastic.
Empty the bleach water from the bucket and refill it with clean water. Wet the sponge in the water and wipe it over the blinds to remove the bleach. Make sure to wipe each blind, removing the bleach completely.
Wipe the plastic dry with a clean cloth. Open the blinds so that any wet areas may dry completely.