some agitators may discolor permanently....now for the best way to dye jeans, at least for me, and I dye them in black....
I have a stainless steel table top washer, motor sits on top and the agitator runs off of it, anywho, a stainless steel pot, with a lid, alone will work the same, HOT HOT HOT WATER, which is why I put mine on top of the stove, BOIL the water and disolve the dye with the addition of about 1 cup of table salt to about 5 gallons of water, some prefer to wet the garment before puting in the dye bath, I don't, just place articles in the water, stir or agitate as needed every 15 minutes or so on a med/low flame for about 1 1/2 hours...
now for me, I take the whole pan outside, and hang the jeans over top of the chainlink fence to drip dry, no rinsing yet, the next day, I run them thru a COLD water rinse in the washer and a spin dry and then to the dryer...some people also prefer a vinegar rinse to lock the color in, your choice
I also prefer the bottle of dye as compared to the powders....for dark color, concentration is the key, thats why its best in the pan, super hot water, and a long soak
usually a cold water, short gentle cycle, high speed spin, is best to keep the color lasting the longest, I get about 5 months of wear before I have to do it again
let us know how you make out!