This is my first time making my own batch of changa and I really hope I'm doing it right

Could you guys help explain a couple things on my mind?

1) As the solvent is evaporating, I've noticed it is leaving red marks on the side of the cup. Am I losing any spice or harmalas? or is it just a color stain?
2) How long should it take for the spice and harmalas to properly infuse with the herb? It has been about 36 hours and the solvent is almost evaporated.
3) Is it important to keep the changa away from light, or is it pretty stable? It is currently in my bathroom on the windowsill.
4) I've read about curing dried changa. Is there any real value to curing it?

1. A little residue will remain. Take a piece of Mullein and rub the cup when its dry or something and smoke it.
2. The absorption happens automatically so as soon as its evaporated its good to go.
3. Yes it's important. Heat, light, and moisture should be avoided.
4. Curing? Just make sure it's fully purged of solvent. Mash and stir the hell out of it and make sure it evaporates all the way.

Thank you for the helpful response House!

If you have the time, I have a follow up question:

Where would be the best place to evaporate the solvent in my future changa batches? My bathroom windowsill does not give any direct sunlight, stays relatively cool, and has a continual flow of fresh air. I take a shower every day but other than that my bathroom is very dry. Every now and then the herbs are exposed to artificial light (the bathroom light), but not for long periods of time (not longer than 40 minutes). Is this an alright place to keep drying my herbs?

Perfectly fine. You can use a fan to speed up the process as well. Light would only become a problem if you left it in a clear glass jar on the window sill every single day.