QB has a default color scheme and shade of color, all you can do in addition is work with your display settings, brightness and contrast

Resolution for 'background issue: 'is there a way to darken the background to make it easier to read and less reflective?' available: Yes.

The background issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the background issue yourself by looking for a resolution described in the article. If it is a complex background issue or you are unable to solve the issue, you may contact us by clicking here or by using other background support options.

For more information about resolving issues related to background in Quickbooks/QBO or to get support for the issue 'is there a way to darken the background to make it easier to read and less reflective?', click the link below: