There's a slight difference in meaning.
must be accepted because it cannot be changed means that this is the reason it must be accepted.
must be accepted: it cannot be changed is making two related statements: it must be accepted and it cannot be changed. But no causal relationship is directly stated, although it might be inferred from the logic. There are probably some other sentences that would have the same form, but the causal relationship would be reversed (i.e. the cause would precede the colon); the relationship comes from the logic, not the sentence structure.
