Little blue bulbs (Scilla etc.) are good with spring blooming magnolias. Otherwise maybe Myosotis - I'd go look at garden centers when the shrub is full out and see what is in season at the same time.

I wonder if the other really is the deep magenta Erica x darleyensis 'Kramer's Rote'. In this picture it doesn't look red enough.

Not exactly an annual but I saw some lovely very pale yellow primroses with dark leaves at the nursery today.........IIRC, they were Primula vulgaris 'Claddagh'. The leaves are almost the exact color of the magnolia's blossoms.

I was tempted :-))

Thanks GG. I’ll look for those. And definitely some bulbs will go in in the fall for next year.