According to this

For Blazers and S-10s (including Bravada, Sonoma, Jimmy, Full-Size) the actual stereo wiring is as follows Constant 12V+ Orange
Switched 12V+ Yellow
Ground Black
Illumination Gray
Dimmer Brown
Antenna Trigger Pink
Antenna Right Front
Front Speakers 4" x 6" Dash
Left Front (+) Tan
Left Front (-) Gray
Right Front (+) Light Green
Right Front (-) Dark Green
Rear Speakers 6" x 9" Side Panels
Left Rear (+) Brown
Left Rear (-) Yellow
Right Rear (+) Dark Blue
Right Rear (-) Light Blue

My question is my front door speaker wires are brown/yellow and light/dark blue but they are not 6" x 9" so can I trust that the yellow is neg and the brown is pos same with the dark blue and light blue and hook up my new speakers following the color code so i dont hook my speakers up backwards. I have a 1997 chevy blazer 4dr LT. Thanks in advance.

 

I don't understand your question. If all you're doing is replacing speakers, then just connect the new speakers to the wires that the old ones were connected to.

 

Thats what I want to do but I need to know what wire is Pos and what one is Neg.

 

The wiring is the same for majority of Chevy/GMC products from 1985 thru 2005 on some models.

The wiring is correct for your truck, regardless of the speakers.