You need to give an array of color in the options for each chart. That's explained on
https://developers.google.com/chart/interactive/docs/customizing_charts
What happens is the same as for the default palette, if you have more data than you have defined colors for then they start again at the beginning.
You can even give the array of colors a variable name in the code and use that in the color option.
usrClr = ['#7CB5EC','#434348','#90ED7D','#F7A35C','#8085E9','#F15C80','#E4D354','#2B908F','#F45B5B','#91E8E1','#2F7ED8','#0D233A','#8BBC21','#910000','#1AADCE','#492970','#F28F43','#77A1E5','#C42525','#A6C96A','#4572A7','#AA4643','#89A54E','#80699B','#3D96AE','#DB843D','#92A8CD','#A47D7C','#B5CA92','#4572A7'];
and then in the options section use
colors: usrClr,