webdriverio: Missing log colors on Travis-CI after migrating from v4 to v5

Environment:

• WebdriverIO version: 5.1.1
• Mode: WDIO Testrunner
• If WDIO Testrunner, running sync/async: sync
• Node.js version: 11.6.0
• NPM version: 6.5.0
• Browser name and version: N/A
• Platform name and version: N/A
• Additional wdio packages used (if applicable): @wdio/spec reporter, @wdio/selenium-standalone service

Config of WebdriverIO

The coloredLogs option does not seem to be documented anymore: https://webdriver.io/docs/options.html.

in wdio.conf.js after migrating from webdriverio v4 to v5, I have kept option:

coloredLogs: true,

Note: but I have changed dot-reporter for spec-reporter.

Describe the bug

With webdriverio v4 on Travis-CI with colours (see https://travis-ci.org/kidoju/Kidoju-Blog/jobs/471099689):

With webdriverio v5 on Travis-CI now without colours (see https://travis-ci.org/kidoju/Kidoju-Blog/jobs/473622155):