<apex:page controller="FlowController" standardStylesheets="True" showHeader="False" sidebar="False">
<apex:stylesheet value="{!URLFOR($Resource.Custom_Classes, 'customclasses/css/myfile.css')}"/>

<flow:interview name="Checker" interview="{!Checker}" finishLocation="{!finishcheck}">
 <apex:param name="orgId" value="{!organizationid}"/>
 </flow:interview>

</apex:page>

<apex:page controller="FlowController" standardStylesheets="True" showHeader="False" sidebar="False">

<style>

.FlowPageBlockBtns.FlowNextBtn{

color:red;
text-align:center;

}
</style>


<flow:interview name="Checker" interview="{!Checker}" finishLocation="{!finishcheck}">
       <apex:param name="orgId" value="{!organizationid}"/>
</flow:interview>

</apex:page>