Cala Lilly Doily - Great Depression Era

Here are two depression era doilies that my great grandmother crocheted. My grandma told me that her mother made these around the time of the great depression. They are beautiful Cala Lilly doilies. I asked my grandma about the color changes. Being an inexperienced crocheter at the time I thought bleach had been spilled on the doily on the right. My grandma said that she just used a different color of thread, probably because she ran out of the color she had. As the years have passed and I have become an experienced crocheter, I understand how my grandma knew it was a color change and not bleach. The color is consistant with the 5 rounds just before the lilly's.