Thank you for using Syncfusion products.
We would like to let you know that, TextBoxExt back color needs to be defined once control initialization process is completed.
We have prepared sample to meet your requirement and it can be downloaded from following location.
Sample Location: TextBoxBorder.zip
Please let us know if it helps.
Sorry for the inconvenience caused.
We have logged a defect report for this case. And it will be fixed in our next Essential Studio Volume 1, 2014 which will be released in February, 2014.
Could you please find the requested sample in below location?
Sample Location: TextboxBackColor.zip
And if you would like to avail patch in version v 22.214.171.124 please contact us using Direct trac so that we can provide patch to resolve this issue.
Please let us know if you need any further assistance,
Thank you for the update. Please let us know if you need any further assistance.