Conditional Inside Conditional

What’s the proper way to do a conditional inside another conditional?

Something like (syntax simplified):

If is_page(1,2) { list titles of page 1 and 2:
         if is_page(1) { name of page 1 in black } else {name in white}
         if is_page(2) { name of page 2 in black } else {name in white}
         }
elseif is_page(3,4,5) {list titles of page 3 and 4:
         if is_page(3) { name of page 3 in black } else {name in white}
         if is_page(4) { name of page 4 in black } else {name in white}
         if is_page(5) { name of page 5 in black } else {name in white}
         }

Basically I need a sidebar link list in two variations, one for page 1/2 and one for page 3/4, and each styled differently.

But I also need it so that the page you’re currently on is a different color from the other links in its respective list.

Any novel approaches is much appreciated.