How can I have a datatype of array in mysql Sequelize instance?

You can use getter/setter functions for this:

favColors: {
    type: Sequelize.STRING,
    allowNull: false,
    get() {
        return this.getDataValue('favColors').split(';')
    },
    set(val) {
       this.setDataValue('favColors',val.join(';'));
    },
}

more info: https://sequelize.org/master/manual/getters-setters-virtuals.html

You can define your field as json:

type: Sequelize.JSON

And then save the data as an array