Brief Answer:
You can color your hair.

Detailed Answer:
Hello,
Thanks for trusting us with your health concern.
You can use a good company mild hair color that you have already used without any allergy during the pregnancy. The hair color is applied externally on the scalp and is not much absorbed through the skin.
Animal studies have shown that the minimal amount of hair color that is absorbed does not affect the pregnancy.
You can consider waiting to color your hair until the second trimester, when your developing baby is less vulnerable. Also, instead of using an all-over hair color, consider a process like streaking, highlighting, painting, or frosting, in which the chemicals have little or no contact with your scalp
Please feel free to discuss further. I will be glad to answer the follow up queries that you have.
Wishing you good health.
Regards.
Dr. Rakhi Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Rakhi-Tayal

---