Style category link depending on category ID

the basic way is to

 #li.cat-item-7
    { color: red; }

Now, change ‘7’ to the number you want, as many times as you want and ‘red’ to the color you want for that category like –

 #li.cat-item-2
    { color: pink; }

    #li.cat-item-8
    { color: green; }