The colours have been selected randomly to avoid association of any one colour with a certain gender or intonation, The Verge reported late on Tuesday.
Previously, Google had numbered its available voices from one to eight, alternating between male and female-sounding voices but the new update would allow users to scroll through from left to right in a carousel layout.
"It's become a bit of an industry norm to associate AI assistants with disembodied female voices. These types of sociological reinforcements by way of technology may have an impact on how we think of and view these personified software products going forward," the report noted.
Google seems to be trying to avoid using only a female-sounding name and voice.
The change has started rolling out for users in the US using the English language option and would continue through the week.
"Google is taking a measured approach here and could be willing to change that approach if it turns out not to have the desired effect," said the report.