Dozens of people gathered outside WK Kellogg Co.'s headquarters in Michigan on Tuesday, demanding that the company remove artificial colors from its plants breakfast cereals in the USA

Kellogg, the maker of Froot Loops and Apple Jacks, announced almost a decade ago that it would remove artificial colors and ingredients from its products by 2018.

This is what the company did other countries. For example, in Canada, Froot Loops are colored with concentrated carrot juice, watermelon juice and blueberry juice. But in the US, the grain still contains artificial colors and BHT, a chemical preservative.

On Tuesday, activists said they would deliver petitions with more than 400,000 signatures calling on WK Kellogg to remove artificial colors and BHT from its cereal. Protesters said there was evidence that artificial dyes could cause behavioral problems in children.

“I am here for all mothers who are struggling to feed their children healthy foods without added chemicals,” said Vani Hari, a food activist who previously pressured Kraft Heinz to remove artificial colors from its macaroni and cheese.

The U.S. Food and Drug Administration says it has reviewed and evaluated the effects of color additives on children's behavior, but believes that consuming these additives does not cause adverse effects in most children.

Based in Battle Creek, Michigan WK Kellogg became an independent company last year when the snack division was founded outsourced to found Kellanova. Kellanova retained the company's international grain business; Froot Loops are now made with natural dyes for markets such as Australia and the United Kingdom.

WK Kellogg said Tuesday that its food is safe and all of its ingredients meet federal regulations.

“Today, more than 85% of our cereal sales contain no colors from artificial sources,” the company said in a statement. “We continue to develop new cereals across our largest brands that contain no artificial colors and offer our consumers a wide variety of nutritious foods.”

Kellogg said it announced its plan to remove artificial colors and ingredients nearly a decade ago because it believed customers were looking for foods with natural ingredients and would welcome the change. However, the company said it found that consumer preferences vary widely across markets.

“For example, our cereal recipes that use alternatives with natural colors are better received in the Canadian market than in the U.S.,” the company said.

Still, Kellogg may need to think again. Last month, California's Democratic Gov. Gavin Newsom signed a bill banning six food dyes from foods in the state's public schools. This makes California the first state in the US to take such a step.

California law bans four of the dyes currently used in Froot Loops: Red Dye No. 40, Yellow Dye No. 5, Yellow Dye No. 6 and Blue Dye No. 1.