last day swim poured some white crystal and some yellow (200 mg each)in hot heptane..
there was very very small particles of junk that sticked at bottom of glass..
swim poured heptane in a small dish and straight to freezer.
24 hours later all the lines on the dish are yellow ! where is my white stuff ?

Have a look at
IMPORTANT: spice color purity fallacy AKA is your dmt ok to smoke ?
and maybe also
..Enough GOO questions! read this..

Current thinking is that an oligomer of DMT forms in the presence of moisture and this causes the coloration. That is to say, the DMT links up into short chains at the molecular level. DMT also has several crystal polymorphs, one of which is yellowish and this may be related to the oligomerisation phenomenon. This has been discussed in some other threads. The oligomerisation does not appear to affect vaporization adversely, and a mini A/B can - but not necessarily always does - produce white crystals again from the yellow material.

wow.thanks for info and link up to that post from endlessness.great !
so i have a question now.if i recrystal a pure powdery white dmt , is it possible stuff changes color to yellow ?

In your OP you said you had white and yellow that you were re-exing did you mix them together into the same solution? If so it sounds like IMO the yellow and white just mixed and you've got your re-exed combined crystal now.

I think this is possible and probably if you look hard enough here on the forum you can find examples of people complaining about this having happened.

yeah you're right.so my final question Is it really need to saturate (evap till milky) the recrystal solvent jar ? today i put 250 mg dmt in 50 ml heptane.it's not saturated ! i gotta evap it or it's ok to cool it down in firdge and next to freezer ?

downward from zero has covered the OP, and to me it makes sense that your colouration is from plant fats and that it would be distributed across all of the included DMT in the solution.
as you would have seen in those links, it is okay to smoke.

in response to your evaporation question:
in my very humble opinion you should not evap any solvent at all, it is unnecessary damage to the only home we have.
what i do is put it straight into the freezer, which will yield less the first time around, but i then reuse the solvent for my next extraction, meaning i am using pre-saturated solvent, so the next time around and from then on i will get better yield, although i would guess not full yield as the warm solvent would not be able to hold as much "new" DMT.
i do have to top up the amount for each extraction as some will inevitably evaporate and be left in containers during the process, but it is never a lot.
what is a few mg of DMT sitting in solvent compared to the money saved and damage to the environment prevented. if you ever decide you REALLY need that DMT stuck in the solvent then you can evap the solvent.

The yellow discoloration is most likely caused by autooxidation of pyrrole. It occurs with tryptamine as well. I've seen snow-white tryptamine, recrystallized with hexanes, start turning yellow in 20 minutes at room temperature. The "fats theory" is dubious; simple tryptamines turn yellow, orange, pink, purple, and every hue in between, due to autooxidation...and heat catalyzes it.

thank you for the correction. consider me educated