1) File --> New --> Spring Starter Project
2) Name --> Calculator
3) Select Maven as Type
4) Click Next
5) Add Dependencies: DevTools, Web, Thymeleaf
6) Click Next, Finish
7) Go to src/main/java --> Create a package called com.example.demo.controller
8) Now, right click the newly created package.

package com.example.demo.controller;


import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class Color_controller {

    @GetMapping("/")
    public String change_color(@RequestParam(defaultValue = "blue") String colors, Model model)
    {
        model.addAttribute("selectedColor", colors);
        return "color"; 
    }

}
Color Picker 
    

        
            
            
        

    




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OUTPUT