Technically you can not change those values. There is no way they would know if you did, so that is the only reason you can get away with it. Changing the size would be altering the ads and against the TOS.
G provides a page for you to edit the colors yourself, all of those values. It's not necessary to change it in the code. (Unless you don't feel like logging back in when you found out you chose the wrong color, like myself, and just edit them manually)
I agree with you! You also see Dp :-- ( Add by google) It's code:-- google_ad_width = 468; google_ad_height = 60; google_ad_format = "468x60_as"; This code describe all story about change dimension.
always try to change every thing form your adsense account - a little mistake while modifying the code can let you kick off from the adsense