There are several reasons that cause you to have the above observations.
1. The light may be different. seem to me the light spectrum cause the earlier picture to look blue while later picture to look purple. This however does not cause change in the intensity of the color. The 2nd reason below is most likely reason for this.
2. initial picture show that the anemone is not as healthy, tentacles are contracted and much shorter. Looking closely at it, you also see the color tip and the body of the tentacle are of lighter color. Seem to have bluish tip and purple body and brown base to me. Need better focus, enlarge picture to tell for sure. The reason why the tentacles are much lighter now, is because the same amount of color got spread out to many times the surface area. I guess that the original picture the tentacles are but a mm or two. Currently tentacles maybe 20-30 mm. If you have the same amount of color but spread out to 30-40time the surface, this would nessesary result in lighter colors. We see this in other anemones. Then they are sick and contracted, their color would look much more intense, but the anemone is not very healthy.
Hope this explain why a few months ago, your anemone look darker, more intense in colors abut lighter now.