Can you post a picture?

Many mophead hydrangeas, especially those that tend to a primarily blue pigmentation, go through a whole range of colors during a bloom cycle. Buds can show as one color, opening to a different then maturing to yet another and finally fading to a fourth. The strongest variations occur from both the bud to bloom stage and from mature to fading. Sky blue, teal, lavender, even a pearly iridescence of all these colors can be present.

Cut hydrangea blossoms purchased from a florist will not necessarily match anything grown in a garden :-) There is just too much variability in coloration with these plants and it is rather easily manipulated in a greenhouse environment in which they are grown for this purpose.

So all this is to say that don't spend all your timing looking for a "teal blue" hydrangea that matches your bouquet. Cuz you probably won't find one :-)) But that is not to say that a homegrown variety may not naturally offer up some of that coloring at some stage of flowering. IME, 'Nikko' is one cultivar that usually offers a pretty wide range of color variations.

We used to have someone that posted about cutting off stems with blooms and then she would put them in water. The water had a die (coloring) in it and, that made the blooms change color. Maybe you could do searches for some keywords in this forum.

We used to do that with Carnations as a kid.