Hair colour, which way to go - Highlights or overall

I have green eyes, and light brown hair which has natural red and blonde streaks in it and I have a yellow skin complexion.

I'm debating whether to do an all over colour in a reddy brown, or have highlights of either red or brown. The only problem with just highlights is my overall hair colour is a mousy light dishwater brown colour! So if I did have highlights i'd still have the original colour underneath. Could i do an all over colour and go for highlights over the top or what?