Options for a heat map in a report

[Blue]

G'day all

Cognos Analytics 11.0.4 on Red Hat Linux viewed in I.E. 11.

I have a report that's used as a dashboard. On the page is a heat map visualisation object. This shows a set of data values (%) at the intersection of two dimensions (row and column).
The vis. only allows to configure colours for max, min, and mid values (e.g. green, red, yellow) then automatically generates the colour between these. Looks nice (see attachment).

The problem is this, green is assumed by the viewer to be 100% yet the vis. will show the max value of the data set as green, e.g. 49%. To the user, 49% should be yellow/ochre. There is no way to set colour boundaries (0-25, 26-50, 51-75, 76-100) in the vis properties.

I have been considering options.
1. modify the vis so that it works as needed - no skills no visJSON and the Vis. Designer tool so will take a while to skill-up.
2. use a Custom Control with JavaScript to render the heat map using D3 - insufficient JS and D3 skills
3. use a cross tab and custom highlighting based on the cell value - ugly

Any recommendation or alternative options out there?

Cheers,

Blue