Answer: You are wise to try to avoid the "instant garden" by filling it up now. I went the instant route a few seasons back because I was too impatient to wait for the garden to fill in, and now I really regret it. I have another large bed that I am building a little bit at a time and I am much happier with the results.
To fill in the gaps while waiting for your perennials to grow, try interplanting with annuals. Here is a list of pink flowering perennials and some annuals. Some are tall in height, some are short: Armeria (Sea Pink), Aster, Dianthus (Pinks), Dicentra (Bleeding Heart), Digitalis (Foxglove), Geraniums, Gypsophilia (Baby's Breath, there are pink varieties), Heuchera (Coralbells, there are pink varieties), Malva, Veronica (Speedwell), Liatris (Blazing Star), Monarda (Beebalm), Echinacea (Coneflower), Paeonia (Peony), Phlox Paniculata, Poppy, Lychnis (Angel Blush), Helichrysum (Rose Icicle), Hollyhocks, Sweet Pea, Celosia, Cosmos, Astilbe, Chrysanthemum, Filipendula (Queen of the Prairie), Impatiens, Iris (pink varieties), Hemerocallis (Daylily, pink varieties), Oenothera (Ozark Sundrops), Penstemon (Beardtongue), Scabiosa (Pincushion Flower), Achillea, Cleome (Spider Flower), Salvia, Xeranthemum (Immortelle), Petunia, and Snapdragon.
Here are some blue/purple perennials and annuals: Agapanthus (Lily of the Nile), Amsonia (Blue Star), Anchusa (Bugloss), Aster, Baptisia (False Indigo), Brunnera (Siberian Bugloss), Campanula (Bellflower), Cantanache caerula (Cupid's Dart), Ceratostigma (Blue Plumbago), Delphinium, Echinops (Globe Thistle), Columbine, Erigeron (Azure Fairy), Geranium (Johnson's Blue), Iris, Lupines, Mertensia (Virginia Bluebells), Lisianthus (Florida Blue or The Blue Rose), Laurentia, Morning Glory (many varieties, lots of blues, pinks and purples), Nepeta (Walker's Low), Lavender, Cleome (Spider Flower), Cosmos, Gomphrena, Nigella (Love in a Mist), Platycodon (Balloon Flower), Scabiosa (Pincushion Flower), Eryngium (Sea Holly), Veronica (Speedwell), Salvia.
Hope this helps!
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