Ahh, poop color. Now we're getting artistic here. I love how these discussions can flow.
Green poop can come from green food (load up on spinach sometime). But remember elementary art class? Green is a combination of the two primary colors yellow and blue. So if it isn't direct from eating green food. Then it will likely be from eating something blue, or blueish. The blue will mix with the stool which will typically have some yellowishness (not alway dicernable) due to the bile, and vwalla, the pallet turns green. The seed thing is interesting, but understandable, since the often contain concentrated substances that could contain the right color combinations.
The dark tarrish brown color mentioned above, is a concern because it indicates possible internal bleeding. As opposed to bright red blood which happens closer to the rectum.
Of course we eat things that contain reds, yellows, and blues, so class...what color does that make? Brown! Very good, you all get an A+
Stool density is basic physics. Oil (including fats) floats because it is less dense than water, but oily/fatty stool should not be a goal. Some fiber can survive the digestive process. It can hold water and air. The right mix of water, oil, and air will produce a stool that is slightly lighter or slightly heavier than water, so it may barely float or barely sink. That is the best, because that is the least difficult on your digestive tract. Hard dry rocks that drop quickly to the bottom, or runny acidic diarhea with floating particals are enemies of the body.
Dense stool is likely from insufficient quantity of oil, water, or fiber in the diet. Or too much time spent in the colon, absorbing the water, releasing the air (please excuse yourself) or compressing the fiber and other waste (which can be proof of peristalsis still working), but I digress, constipation is covered elsewhere on the site. We were discussing color here.
Well this has been fun, I think I'll go paint a picture now