I recently acquired a beautiful tie-dye shirt. How do I wash it so the colors will not fade?

Instructions
Things you'll need:
Pre-treatment spray
Mild laundry soap

Store-bought tie-dye

Step 1: Read the care label. Most tie-dyed fabrics and garments can be washed in warm or cold water. Wash your garment accordingly. If there are any stains, spray them with pre-treatment spray and let the spray soak into the fabric for a few minutes. Use a spray that does not contain any bleach; this can harm the color in the fabric.

Step 2: After treating any stains, place the shirt in the washer and add detergent. Be sure to use a gentle soap that contains no bleach.

Step 3: After washing the shirt, hang it up to air-dry or lay it flat to dry. Air drying helps keep colors bright and reduces fading.

Homemade tie-dye

Step 1: Pre-treat any stains as needed. Let the garment sit for 5-10 minutes after spraying to let the spray soak into the fabric.

Step 2: Handwash the shirt in cold water. Let the shirt soak in a bath of cold water with washing detergent for 10-15 minutes. Using your hands, gently rub the fabric together to remove dirt and grime. Wring out water and soap, then rinse the shirt in cold water to remove any lingering soap. Wring out all excess water.

Step 3: Let the shirt air-dry to preserve the color. Iron on a low setting if needed.

https://www.goodto.com/family/things-to-do/tie-dye-t-shirts-538184

Hope this works.

A technique widely used in the 60s for tie-dyed clothing was to soak the item in salt water overnight before use. This helps to set the colors, and reduce the problem of fading. Avoid heat - wash in cold or warm water, do not tumble dry, air dry in shade rather than sunlight as sunlight is a powerful bleaching agent!