How can we change the colour of Visualforce table dynamically?

Hello Mohit,

You can assign CSS classes dynamically based on the picklist value using styleClass attrubute:

Try below code

<style>
.errorClass {
background-color: red;
}
.normalClass {
background-color: green;
}
</style>

<apex:pageBlock>
<apex:pageBlockTable value="{!testObjectList}" var="item">
<apex:column value="{!item.name}"
styleClass="{!IF(item.status__c == 'Critical','errorClass','normalClass')}"/>
<apex:column value="{!item.status__c}"
styleClass="{!IF(item.status__c == 'Critical','errorClass','normalClass')}"/>
</apex:pageBlockTable>
</apex:pageBlock>