here is an interesting css code for you who want to use it



/******************************NEW*********************/
.rainbow-text {
 animation-duration: 3.115s;
}
/*fb8532*--000000*/
/*2188ff--2846F0*/
/*ffd33d--1DB30F*/
.rainbow-text {
 background: linear-gradient(43.13deg,#ffd33d 0,#000000 90%,#ea4a5a 90%,#8a63d2 90%,#2846F0 90%,#34d058 90%,#1DB30F 100%);
 background-size: auto;
 background-clip: border-box;
 background-clip: text;
 display: inline-block;
 color: transparent;
 text-fill-color: transparent;
 -webkit-background-clip: text;
 -webkit-text-fill-color: transparent;
 animation: shine 6.28s alternate infinite;
 animation-duration: 6.28s;
 background-size: 300%;
 font-size: 30px;
}

@keyframes shine {
 0% {
  background-position:200% center
 }
 62.8% {
  background-position:100% center
 }
 100% {
  background-position:200% center
 }
}
/******************************END*********************/

Found at:https://werner-zenk.de/

Installtion so here:

echo "<center><span class='rainbow-text'><strong>Your text</strong></span>


thanks lg