Let's say that you have a dynamic list with items coming in from a database. For each item in the list, you want the background colour to be different.
Firstly, create an array of colours.
$colours = [
'#505d6a',
'#832b67',
'#612b83',
'#2b3f83',
'#2b8367',
'#0096b6',
'#1fa400',
'#ff7e00',
'#990000',
'#707d00'
];
Then, to loop through each item and assign the next colour in the array AND THEN start the colours from the beginning again if there are more items than colours:
$i = 0;
// Lets assume my items are stored in an array called $items
foreach ($items as $item) {
echo "<div style='background:" . $colours[($i % count($colours))] . ";'>";
echo $item;
echo "</div>";
$i++;
}