Google has changed the color of its ad tag icon from yellow to green, Adage India reports.

This seems like a minor change until you factor in that marketers spent $20.5 billion in search advertising in 2015, an 8% increase from the previous year, according to the IAB. Even a small increase in clickthrough rates would translate into millions for Google.

A Google spokesman has said that the color change showed "absolutely no difference" in clickthrough rates after testing it on 5% of its user base back in April. Though that could change for better or worse as the color swap is launched worldwide.

"We regularly test ways to improve the look and feel of our search results page," Google said in a statement. "We've been experimenting with a green search ad label and have decided to roll it out based on positive feedback from users and advertisers."