' Rainbow Neutral - ICE - Sentry - Code Gate - Barrier '

I'm assuming, since this ice has all three usual ice types, that the runner would need an icebreaker or icebreakers that can break all three types of subroutines. Correct?

Incorrect.

It is all three, so an ice breaker able to go through any of the three could break the subroutine. Hence the lower cost compared to Bastion.

OK, thank you!

Rainbow provides a nice cheap block to the runner in the early game forcing them to go find some form of icebreaker.

Its downside is that any standard breaker (fracter, decoder, killer or AI) can get through it, but as the game progresses no amount of ICE is likely to guarantee to keep the runner our indefinitely.

But being strength 4 means that it does tax the runner slightly more throughout the game, Compared to other cheap EtR ice (Enigma, Rototurret, or Wall of Static) it'll cost the runner about 3 credits to run around each time.

Also has an interesting interaction with Unorthodox Predictions, in that it becomes unbreakable no matter what the corp chooses.