Is there a way to apply a rainbow emission on a Standard Material?

Questions
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1

I must implement a model that has a rainbow emission on itself, but, as I have noticed the Standard material only takes a single color as an emissive value at a time, I have a rainbow map I must implement in order to recreate my model’s appearance but, as I have noticed it seems like its not possible.

I am currently working with React and ThreeJS using react-three-fiber, I am not sure if that’s relevant for my problem but I’ll mention it anyway.

<meshStandardMaterial
                        //color={"#FFFFFF"}
                        map={modelMap}
                        normalMap={modelNormal}
                        envMap={environmentMapTextureModel}
                        envMapIntensity={3}
                        roughness={0.2}
                        metalness={0.5}
                        side={THREE.DoubleSide}
                        emissive={'#ffffff'} // This emissive only takes 1 color, if you put a texture it won't work at all
                        emissiveMap={emissionMap} // This is meant to delimit which parts of the model should emit light and which ones shouldn't, as long as I know
                        emissiveIntensity={0.05} // the emission's intensity
                    />

How can I achieve this goal? Can it be done using shaders and then how? I’m not very knowledgable in the subject of shaders.

Thanks in advance for any help.