Do you have a tester?

my experience with 3 way switches is that its not easy at all for someone to explain to you how to do it. go and get a book that explains it and has illustrations. thats how i did mine, not knowing much about electricity and def not knowing how to wire a 3 way. home depot's wiring 1-2-3 is what i have and was very helpful.

You don't have enough wires for the light to be between the switches. Tell us all the wires in the switch boxes. Note which wire is conencted to the common screw. It will be the black screw or marked common on the switch. Upper left, lower right is useless info.
Also it appears you might be on conduit system. Please confirm that.

i know when i wired mine, i went power source to the firs switch, then 3 wire to the next switch then 2 wire to the light. how exactly it is wired though i am not sure, i went by the book i got. thats the best recomendation i can give.

is this existing or new construction/remodel?

Sometimes electricians carry the 3-wire from one switch to the other via the light's box, to make a shorter run or just because it's convenient to route that way. If that's the case, then there should be a grand total of eight wires (excluding grounds) entering the light box:

* 2 hots (one black, one some other color) and a neutral (white) from the first switch.
* 2 hots (one black, one some other color) and a neutral (white) from the second switch.
* A hot and a return (not a neutral) from the second switch. One of these should be black and one should be some other color. However, if the circuit is romex, one of them will probably be white; if so, it should be painted black or have black tape on it near the end. These would be the two wires connected to the light fixture.

What it sounds like to me is that the light box is not really "between" the two switches in terms of how the circuit is routed, even though it may be physically in between. My guess is that the yellow is the switched hot, and the white and green are what you expect. I'm not sure what the always-hot black is doing there. Possibly at some time in the past, there was a ceiling fan installed there with a light, and the yellow was connected to the light lead of the fan so the light could be switched on and off with the wall switches. The black might have been connected to the motor lead, and the fan turned on and off via its own pull chain. That's kind of unorthodox, but in an older installation, it wouldn't surprise me.

* 2 hots (one black, one some other color) and a neutral (white) from the first switch.
* 2 hots (one black, one some other color) and a neutral (white) from the second switch.
* A hot and a return (not a neutral) from the second switch.

Assuming the power comes into the first switch, the first statement is correct, the second statement has the white wire painted black and is the hot from the second switch, the third statement is not neccessary.

I remember the layout by realizing that neither switch is an on/off switch but rather an either/or switch. The first switch energizes either the black or red wire traveling to the other switch, the second switch receives the energy through either the black wire ot the red wire. If both switches are identical and installed right way up , then the light will be on if one switch is up and the other down, if both switches are up or down the light is off.