Code:

<script>
var text="newbie là số 1" // text
var speed=80 // toc do chuyen mau
// ********** LEAVE THE NEXT BIT ALONE!

if (document.all||document.getElementById){
document.write('<span id="highlight">' + text + '</span>')
var storetext=document.getElementById? document.getElementById("highlight") : document.all.highlight
}
else
document.write(text)
var hex=new Array("00","14","28","3C","50","64","78","8C","A0","B4","C8","DC","F0")
var r=1
var g=1
var b=1
var seq=1
function changetext(){
rainbow="#"+hex[r]+hex[g]+hex[b]
storetext.style.color=rainbow
}
function change(){
if (seq==6){
b--
if (b==0)
seq=1
}
if (seq==5){
r++
if (r==12)
seq=6
}
if (seq==4){
g--
if (g==0)
seq=5
}
if (seq==3){
b++
if (b==12)
seq=4
}
if (seq==2){
r--
if (r==0)
seq=3
}
if (seq==1){
g++
if (g==12)
seq=2
}
changetext()
}
function starteffect(){
if (document.all||document.getElementById)
flash=setInterval("change()",speed)
}
starteffect()
</script>

demo

var text="c5zone là số 1" // text
var speed=80 // toc do chuyen mau
// ********** LEAVE THE NEXT BIT ALONE!

if (document.all||document.getElementById){
document.write('' + text + '')
var storetext=document.getElementById? document.getElementById("highlight") : document.all.highlight
}
else
document.write(text)
var hex=new Array("00","14","28","3C","50","64","78","8C","A0","B4","C8","DC","F0")
var r=1
var g=1
var b=1
var seq=1
function changetext(){
rainbow="#"+hex[r]+hex[g]+hex[b]
storetext.style.color=rainbow
}
function change(){
if (seq==6){
b--
if (b==0)
seq=1
}
if (seq==5){
r++
if (r==12)
seq=6
}
if (seq==4){
g--
if (g==0)
seq=5
}
if (seq==3){
b++
if (b==12)
seq=4
}
if (seq==2){
r--
if (r==0)
seq=3
}
if (seq==1){
g++
if (g==12)
seq=2
}
changetext()
}
function starteffect(){
if (document.all||document.getElementById)
flash=setInterval("change()",speed)
}
starteffect()