Hi there! I don't know why I haven't posted much around here but I should.
I see you have lopped off your points there, and I have many twins to your pointless square! Lol* It looks like maybe you had an issue with measuring...I haven't made this block before, but it looks as if you set the center square on point by sewing smaller squares to each corner and then when pressed to the right side it makes for triangles on each corner turning your square on point. If this is what you are doing, be sure that you are not trimming down the green after you've finished pressing. You will trim down your seam allowances in the back, but do not "square up" your square at all. It may look wrong, but all edges of your square will have 1/4 an inch of green beyond your black square points, that will be your seam allowance, so when finished sewing on the logs around it, you will have a perfect four pointed square in the center.
If that does not help, I would also check that you are measuring your black square correctly when cutting, and your lighter green squares...if either one is cut wrong you'll either "float" or "lop off" your square! :) (Can you tell I have a few pointless squares and triangles floating around my scrap bin?)
As a few others have mentioned, be sure your 1/4 inch guide, whatever you are using, is accurate. Even if you are using 1/4 inch foot as a guide, you will want to double check where exactly you should be lining your fabric up when sewing. There are many ways to check, but I take one of my smaller rulers, bring my needle down and just touch it to the first 1/4 inch line in on the ruler. Then I see what part of my 1/4 foot the edge of the ruler aligns with...a scant 1/4 seam for my machine and foot, is just at the outer edge of where my feed dogs come up, and does not extend even a thread past my foot.
As for colors, it's all subjective. There is such a wide range of styles and tastes, I don't believe any one person could tell you what does and doesn't go...what matters it what your feeling is, and if you are pleased with the color combination, then it's a go! :) I can tell you I have seen many award winning quilts that had color schemes I wouldn't touch with a ten foot pole! :) There is an infinite combination of colors and values that can be used in an infinite number of ways. Experiment! :) (I like your combination of greens by the way, it is very authentically Amish in my opinion :) lol*)
I hope I haven't rambled too much and that maybe this helps! :)
Good luck! :)