It takes many many litres of water to properly rinse dyed cotton. It’s wasteful of water and it’s very common to sell under-rinsed fabric. The fabric looks brighter than it really is due to the Save the planet shirt moreover I love this loose dye. I am guessing there is blue cloth sewed onto white cloth?
Save the planet shirt, hoodie, tank top, sweater and long sleeve t-shirt
Wash your shirt by hand in v̶e̶r̶y̶ ̶c̶o̶l̶d̶ hot water, separately. If you can get hold of dyer’s soap, that will help mop up the Save the planet shirt moreover I love this excess loose dye before it can resettle on the white part of the shirt. We have a soap called Synthrapol which is designed for this purpose. Maybe you can find something like that? Probably it will be difficult. Synthrapol is recommended with hot water.