my parents are getting older and they want to plant some plants in the borders that give colour and come up every year

Depends whether yoiu want shrubs or perennials - but I have to say, this does sound like a thinly veiled exam question again...

Hello Sharron welcome to GOY.
Can you give us more information so we can help you such as full sun or shade? climate, soil type? high or low maintainance? depth of border? is it against fence? all year round interest or just summer colour? some likes/dislikes?

I agree Bamboo exam question - or rather practice exams... if you would just be honest and tells us this it would be much easier to help you!

Getting older ? I am 82 and I might look older but I still feel younger than my own children now are !
I suggest that in their border they have a couple of tomato plants and a small wigwam of runner beans. Put the flowers in the spare places. I am sure the watching and growing of the veg will give them loads and loads of pleasure.