ENH: switch lim colors to blk/org from yel/yel

[ZLLentz]

Description

Switch the limit indicator colors to something more visible for the positioner widgets.

Motivation and Context

Many justified complaints about yellow -> brighter yellow being impossible to see for many users/screens

How Has This Been Tested?

Interactively only

Where Has This Been Documented?

slack thread, so far, release notes later

Screenshots (if appropriate):

old:

new:

Pre-merge checklist

• Code works interactively
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Code has been checked for threading issues (no blocking tasks in GUI thread)
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[ZLLentz]

tests broken by some upstream library change, will untangle in a separate PR

[patoppermann]

Good choice of colors.

[ZLLentz]

I'm going to merge this and apply it to dev_conda, then come back later for the more general typhos build issues