RFR: 8266247: Swing test bug7154030.java sometimes fails on macOS 11 ARM

[Alexander Zuev]

Change background and foreground colors to white and black to avoid color shift problems.

-------------

Commit messages:
 - 8266247: Swing test bug7154030.java sometimes fails on macOS 11 ARM

Changes: https://git.openjdk.java.net/jdk/pull/8313/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8313&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266247
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8313.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8313/head:pull/8313

PR: https://git.openjdk.java.net/jdk/pull/8313