The following code creates a rotating color change animation. It changes the color in a circle in a text element.

Add the colors in code

background: conic-gradient(from 0deg, #00f5d4, #7209b7, #3a86ff);

Control the time of animation from code line 

animation: rotateGradient 5s linear infinite;

and control the rotation gradient colors in the code

0% { background: conic-gradient(from 0deg, #00f5d4, #7209b7, #3a86ff); }    100% { background: conic-gradient(from 360deg, #00f5d4, #7209b7, #3a86ff); }

CODE

.css-tutorial {
   background: conic-gradient(from 0deg, #00f5d4, #7209b7, #3a86ff);
   -webkit-background-clip: text;
   -webkit-text-fill-color: transparent;
   background-clip: text;
   animation: rotateGradient 5s linear infinite;
}
@keyframes rotateGradient {
   0% { background: conic-gradient(from 0deg, #00f5d4, #7209b7, #3a86ff); }
   100% { background: conic-gradient(from 360deg, #00f5d4, #7209b7, #3a86ff); }
}