[Accessibility] Combo boxes labels not read in Selected Layer Display tab

[aphelionz]

Steps to reproduce (assumes ChromeVox or similar)

1. Open Kibana in a new tab
2. Tab to Canvas
3. Select an existing or create a new canvas
4. Select a layer or create a new eleemnt
5. Tab through the fields on the "Select Layer" panel on the right

Actual Result
6. The announcements of many elements are simply "drop down" or "button"

Expected Result
6. Labeling should be consistent and informative. In the above image, the announcements should be "Select a Shape", "Fill", "Border", etc.

#24159 Kibana 6.5 Meta Issues
#23534 Canvas Accessibility

Relevant WCAG Criteria: 3.3.2 Labels or Instructions

[elasticmachine]

Pinging @elastic/kibana-canvas

[PhilippBaranovskiy]

The good point is here to discuss whether it should announce the name of the focused color (in the palette popover) as well as the name of a chosen color.
Should it announce the name of the color rather than the HEX color code?

Example: the user is focusing on the "Fill" section, next tabs to the color icon. Before activating that, (s)he should know what the current color is set already.

@timroes @aphelionz

[rayafratkina]

We decided that standard colors will read: Kibana Teal, Kibana Yellow, Kibana Pink, Kibana Blue, Kibana Green. The saturation level will be read out as 1, 2, 3, 4. So the standard colors will be announced as "Kibana Yellow 3" or "Kibana Green 1".
Is user enters a custom color, it should be read as a hex code.