Select any drop-down menu option and perform the corresponding action

Help: Select any drop-down menu option and do the corresponding action?

Excuse me: How to implement this operation with PHP program, please give me a hint. I'm thinking of using $_post to receive the Select value (), what JavaScript is needed to determine what, and finally change the color with switch implementation. I don't know if it works. It's not clear how JavaScript is judged. Thank you!

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If you just want to change the color of the page elements, why bother PHP with JS is enough

HTML Code

Please change the text color---black------red---  ---green------blue------yellow---
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Includes the jquery library, under Baidu

With JS can be, similar to the following:
  
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     JScript code 
    
  new document  
      
      
      
      Please change the text color  ---Black--- ---red--- ---Green--- ---Blue--- ---yellow---  ssss sdfsdf sddddddddddd 
 