how can i automatically generate the dimensional constrains while create the sketch?

Hello Friend,

I don't think so there is an option for Generate dimensional constrains automatically while creating sketch.

We can create dimension automatically after create the sketches by AUTO CONSTRAIN option.

Answer for your Second Question is.

Go to TOOLS -> OPTIONS -> PARAMETER & MEASURE -> CONSTRAINTS & DIMESIONS

Here you can change the colors of the dimension line,size and all.

Hope my answer will help you.

Thanks
Vinoth