Gradient on GLSL with variable number of colors?

Question

Graphic arts

How to make such a gradient?
There are no problems with the usual option for full screen and two colors (example of a radial one)

attribute vec2 position;
uniform vec2 resolution;
varying lowp vec2 coord;
void main(void) {
vec2 np = position/resolution;
np.x=np.x*2.0-1.0;
np.y=1.0-np.y*2.0;
coord = np;
gl_Position = vec4(np, 0.0, 1.0);
}

varying lowp vec2 coord;
uniform mediump vec3 color1;
uniform mediump vec3 color2;
void main(void) {
lowp float inten = sqrt(coord.x*coord.x+coord.y*coord.y);
mediump vec3 color = color1 * inten + color2 * (1.0 - inten);
gl_FragColor = vec4(color,1.0);
}

How can I make color start points and a variable number of them?
For example, the above is standard for 0% color1, 100% color2, and it is necessary with support for intermediate colors