Completely normal. This is why experienced growers don't harvest by pistil appearance. Sometimes they go brown early. Sometimes, also, pistil color is affected by the application of insect repellents and nutes. I'm sure there are others here that can give you an excellent botanical explanation for pistil color change. I'm not a botanist--just an old boy from Maine who grows a little herb.
the color and type of the Resin crystals. Depending on how you want it im not 100% sure if this is correct some want 50% amber and 50% cloudy, you need a magnifier, i believe a 10X jewelers? please correct me if im wrong
Bit more than 10X - like 40X will do - the one I use (a Nexxtech pocket microscope) does 60 or 100 (too much). Check out you local Source/Circuit City or Radio Shack - it cost me $20 IIRC. When to harvest is an art, and as such highly subjective. The first stage of trichome development is clear and pointy. Then they get a bulbous tip (round head). Then they get cloudy and then they turn amber. For more cerebral ('headies") you want more cloudy than amber (earleir harvest - say 80/20). For more stoney, bodybuzzy couchlocky go for more amber. The thing is, that headies come with a price - slightly smaller buds as they haven't been allowed to mature as long (why I personally don't recomend 100% cloudy).