Change color gradient to differentiate between observations that are 1 vs 2 days old

[scottveirs]

The current color palette used to indicate the age of observations makes it difficult to differentiate between 1 vs 2 days. As a user of the acartia.io landing page, I would like to be able to clearly see the distribution of the most recent sightings in the data cooperative (ie. that are <1 day old).

Example screenshot showing current color palette gradient:

Proposed solutions

1. Switch from a gradient to color boundaries that change every time an observation ages by another day.
2. Change the gradient so that there is more change between observations that are about 1 vs about 2 days old.

[scottveirs]

Moving this to the salish-sea/acartia fork here, and closing.