This document summarizes several studies on color image encryption techniques for secure transmission over the internet. It discusses the need for encrypting images due to privacy concerns when transmitting data over insecure networks. Several encryption methods are summarized, including approaches using hyper chaos, pixel bit scrambling, sharing matrices combined with encryption, logistic mapping with phase encoding, multiple image encryption using compressive imaging, and a fast encryption scheme using environmental noise. The techniques aimed to improve security, efficiency, speed and resistance to attacks. While most achieved their goals, future work is needed to address transmission speed, protection against all attack types, and reducing computational costs for some algorithms.