Pulmonaria (Lungwort) is one that springs to mind. I think they open pink and turn to blue. The 4 o'clocks that have multiple colors on one plant always blow my mind for some reason, too.

Pink forget me not, shows signs of pink and ages to a purplish color, then you get blooms at different times, quite pretty that way, mix of pinks to purple..

Dragon's Blood Sedum
(Evergreen)

Deep, Red-Maroon leaves in winter changes to green with maroon stems in summer. It's tiny and blooms in late summer. Bloom color varies as do the leaves depending upon the variety you get. My Dragon's Blood Sedum fits the name - Has reddish flowers in summer and deep Maroon leaves all winter and spring.

It likes full sun and good soil, but soil that drains well. The more sun it gets, the deeper the red tones in the leaves.

The LINK below gives you accurate images of Dragon's Blood.
I cannot find the photos of mine, but it looks just like their maroon one.

~Annie

Here is a link that might be useful: Dragon's Blood pics and info

Rose 'Mutabalis' really pretty

Confederate Rose (Hibiscus mutabilis)
Yesterday, Today, and Tomorrow (Brunfelsia calycina)

How about Joseph's Coat roses? The blooms change coolers from orange to red to pink to yellow. You may have all those colors on the bush at once. I am dazzled every day to go out and find the rose a different color than it was the day before - it's like magic!

I have a miniature rose that does that too. It's called 'Carnival'. It is only 2 ft tall and the blooms are about an inch or two wide. Colors are orange, medium pink, light pink, yellow and pale yellow. Blooms off and on from late Spring thru Fall. Smells sweet too. The blooms end up almost white. Can be grown in a container.

Love snapdragons - they are so magical. They talk. We used to push on their sides as children when my grandmother walked me thru the garden. I can really remember that experience.

There's always lantana which would be an annual for you. I bought another beautiful color-chaning annual this year, Verbena 'Obsession Apricot.' It's an eye-catcher!

Borage flowers turn from blue to pink after pollination.

Perennial blue flax (linum narbonense) 'Heavenly Blue' can be grown from seed. It blooms in the morning, then the flowers are gone as the day heats up. The next morning, they are magically blooming again. They don't change color, but the bloom sequence is fairy like. I love this flower and it reseeds. Taking little room, you can weave these through other plants. I have some at the feet of roses.

Linaria 'Canon J Went' is a toadflax that reseeds a lot, but the pale pink delicate spires on blue foliage is so nice. The blooms are constant and they look like teeny tiny snapdragons.

My allium christophii bloomed back in April, but I still have the sparkler looking remains standing in the garden. I use wooden skewers to keep them upright at this stage. Some folks paint them, too!

If you could use yellow and burgundy (looks good with blue), then I highly recommend coreopsis 'Redshift' as it changes from pale yellow and gradually turns more burgundy into autumn. It's about 3 feet high, but mine are very upright in full sun. I don't deadhead these and they just keep on blooming.

Cameron

Here is a link that might be useful: Heavenly Blue Flax

Very intersting quesion LL! I do love roses that change color- they are so much more interesting than some monochromatic roses that are only one color from start to end.

One of my FAVORITE "perennials" that changed color was Erysimum (wallflwoer) 'Pastel Patchwork'. As the flowers aged they turned from mauve/purple to coppery orange/apricot. Truly stunning! Wouldn't you know it, the very year I got rooting hormone to try and propigate more from cuttings (just in case it were to die out) it dies. LOL.

Achillea (Yarrows and Millfoils) are known to change colors. Certain kinds of newer coneflowers do the same I think.
I have a Dianthus (sweet william- from a mix) that changes from pink to white as flowers open. There is a lilac called 'Beauty of Moscow' that has pink buds and open to double white flowers.

Euphorbia polychroma/epithymoides- the foliage near the little flowers flush a chartreuse then fade to green.

Tellima grandiflora (Fringe Cups- native to this state) start out a pale greenish white and fade o a lovely raspberry color. Related to coral-bells but easier to grow.
Ok, think I am done now ;-D
CMK

My favourite are Pinky Winky Hydrangeas. I know they are not technically flowers...but I love them. The large white panicles open in mid to late summer, and as summer turns to fall the florets at the base of the panicles turn pink. The flower panicles continue to grow, producing new white florets at the tip.

So many great ideas! Thank you all and I'll start checking zones and my non-toxic list...but some of these sound perfect for the fairy garden :)

Many types of hydrangea change color. For sun, there are the P.G. hydrangeas that change from cream to pink. My current favorite is Little Lamb, but my new favorite might be "Strawberry Vanilla".

For shade, there are the the mophead and lacecap hydrangeas. Many of these start out either blue or pink, depending on your soil type, and then turn to a blend of colors, ending up mostly green. My favorite of these right now is "preziosa", which starts out cream, turns lavender, then turns dark red.

Here is a link that might be useful: hydrangea preziosa

These have already been mentioned but for me, Pulmonaria (lungwort) is one of my all time favorites and my Wonderful Wompee Yarrow (pink to white) and my Strawberry Seduction Yarrow (red to yellow) changes as the blooms age as do my Hydrangeas

I have an annual called Silene Ameria that I started from seed that started as a pale pink and got dramatically darker as the blooms age. They are very bright pink now.
I also have a cransebill geranium that bloomed white and then faded to pink but that's done blooming now.

~Andrea