RFR: 8326027: Comparing buffered images of white background frame fails in Mac

[Tejesh R]

On analysis of captured image, it is observed that there are few pixels which vary slightly w.r.t to expected color. Hence tolerance is included in color comparison. 
Tested in mach5 multiple time and its green.

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Commit messages:
 - Update with tolerance value for color comparison

Changes: https://git.openjdk.org/jdk/pull/20760/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20760&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326027
  Stats: 11 lines in 1 file changed: 7 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20760.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20760/head:pull/20760

PR: https://git.openjdk.org/jdk/pull/20760