how to get color of the customtab

hello,

i am using asp.net using c# and sfapi.
i just want to know how can i get the colour of customtab which we use in salesforce.com.

i am not getting that by describeTab or describeSObject function.
Is there any solution on this to get the colour of the customtab or the theme of the customtab , we use in salesforce .

thanx.