That's the color in my experience.
Last time I made Ferric Oxalate, I used a 600ml beaker with 25ml water, 6.7g B&S Ferric Ox, about 1g EDTA and a 1000ml water bath at 150 degrees. I swirled the solution around in the bottom of the beaker, submerged in the hot water. Went into solution in about 15 minutes. Easiest time I've ever had with this step.