It is not uncommon for some Kalanchoe to vary in color. The first photo shows a plant grown under commercial conditions to induce flowering and be attractive enough to attract a customer.

Some Kalanchoe flowers change slowly as they mature, so that a yellow flower may develop a strong orange or red tint over a period of a week or so.

What is the time period between the two photos? If it is a very short time, then it may be the difference in light and humidity from its development to the place where you have it growing. It is my experience that the wonderful condition of the newly purchased plant does not persist, and when the next flowering period comes around (generally a year later), the plant will be less vibrant and the flower color may or may not be somewhat changed. Yale

There is about 2 months between pictures. So would less sun produce a paler color?

I bought two bright yellow mini kalanchoes and planted them outside in sun, using a miracle-gro potting soil, in hanging coconut baskets. They are surrounded by a variety of succulent clippings (from bigger ones around my garden). The kalanchoe flowers are now a beautiful sunset orange and the clippings are growing big and happy.

I get occasional refugees that were commercial blooming plants and I've struggled to make them happy. I wish I knew what their second bloom was like! I'm about to prune and repot one. I'm not sure what medium to use though.

I have had this happen on 2 different plants now. One had bright yellow blooms first and then later blooms were more peach or even salmon colored. And then a purple one gave pink blooms later.

Also the yellow then peach plant has done that the last 3 years. First flowers will be bright yellow then later ones darker.

I have just discovered this effect, also. I bought a white flowering plant. it was quite striking. As flowers aged they acquired a bit of pink colouring. i am now discovering that old flowers are turning yellow! Some new buds are showing through as white, and some as white at the base with a strong pink at the points. It is putting on quite a show.