Answer: I believe the name you are thinking of is perhaps "carpet bedding" which originally referred to ornate patterns done with foliage plants in Victorian times but now is used to refer to patterns made with flowering plants as well.
One very nice blue often used successfully in such patterns is ageratum, which is available in several heights and shades. My personal favorite especially for a hot or windy and consequently drier site, however, is salvia farinacea "Victoria" which would combine well with the marigolds and perhaps a white alyssum or, if more height is desired, a white petunia. A very pale silvery gray such as that of a Dusty Miller type plant can also look good in place of pure white. These plants will all take sun and some wind but excessive water will cause nearly any plant to rot at the roots, so you might consider realigning or refitting your watering system to account for the runoff caused by the slope. Good luck with your project!
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