package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReaderSize(os.Stdin, 1<<20)
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	var t int
	fmt.Fscan(in, &t)
	for ; t > 0; t-- {
		var n int
		fmt.Fscan(in, &n)
		a := make([]int, n)
		for i := 0; i < n; i++ {
			fmt.Fscan(in, &a[i])
		}

		allSame := true
		for i := 1; i < n; i++ {
			if a[i] != a[0] {
				allSame = false
				break
			}
		}

		if allSame {
			fmt.Fprintln(out, "NO")
			continue
		}

		s := make([]byte, n)
		for i := 0; i < n; i++ {
			s[i] = 'R'
		}
		for i := 1; i < n; i++ {
			if a[i] != a[0] {
				s[i] = 'B'
				break
			}
		}

		fmt.Fprintln(out, "YES")
		fmt.Fprintln(out, string(s))
	}
}