How can I remove grease stains off custom blinds?

Talk with the place you got the blinds from or their internet site may have care information, If you know what kind of fabric it is ..Google how to remove grease stains from that fabric name. You might want to identify the type of grease as well. Also you may want to call a furniture

re-posturing company and ask them.

Have you tried water with some dish soap?

If they are fabric it is tricky. Use a small amount of WD40 right on the spot, then use a baby wipe to gently wipe the stain and WD40 off. Air dry.

For fabric blot it with a small amount of blue dawn and water

If the blinds are vinyl or a similar product, you can always take down the blind. Place it in your bathtub and cover it with a solution of water and Dawn dish washing liquid) OR Scrubbing Bubbles. Let it soak for a bit. Using a brush, scrub at the area, taking care to not bend the blind sharply. Stain gone? Dry and rehang. Not gone? Another option would be to check Pinterest with the same question naming the brand of blind or the product it is made from. Good Luck

Depending on the material, I would use Dawn dish soap. I use it to get out grade stains all of the time.

Check the label for cleaning instructions or call/google the manufacturer requesting proper care. Best of luck.