Ctx 15 pl5 monitor seems to be stuck in a default 16 color mode and wont allow me to change it. Suggestions?

The monitor has no influence here - something is wrong with your video card: either its driver is missing (or corrupted) or the video chip has failed.
Uninstall all the drivers for the video(except the generic VGA one), from Programs and Device Manager
http://pcsupport.about.com/od/windows7/f/open-device-manager-windows-7.htm
and reboot several times then go to Dell
http://support.dell.com/support/downloads/index.aspx?c=us&cs=19&l=en&s=dhs
select your pc and get the correct driver.
If that doesn't fixes it then the video chip has failed, you will need to buy a new video card.

Restart the computer
2 While the computer is loading, press "F8" key on the keyboard right before the
computer reads the hard drive or press the "F8" key multiple times in 1 second
interval until the "Windows Advanced Options Menu" appears on the screen
3 Under "Windows Advanced Options Menu", using the arrow key on the
keyboard, select "Enable VGA Mode" then press Enter. Select "Windows 2000
or Windows XP" for your operating system.
4 Wait while the computer is loading and once the computer finishes loading,
5 Right Click anywhere on the blank area on the desktop then click "Properties"
6 Click on "Settings"
7 Click on "Advanced"
8 Click on "Adapter"
9 Click on "List All Modes..."
10 We recommend that for 15" LCD's select 1024x768, True Color (32 Bit) 60
Hz or 1024x768, High Color (16 Bit), 60 Hertz; For 17" & 18" LCD's select
1280x1024, True Color (32 Bit), 60 hertz, or 1280x1024, High Color (16 Bit)
60 Hertz, or
640x480, 256 colors, 60Hertz or 75Hertz
640x480, High Color (16 bit), 60Hertz or 75Hertz
640x480, True Color (32 bit), 60Hertz or 75Hertz
800x600, 256 Colors, 60Hertz or 75Hertz
800x600, High Color (16 bit), 60Hertz or 75Hertz
800x600, True Color (32 bit), 60Hertz or 75Hertz
1024x768, 256 colors, 60Hertz
1024x768, High Color (16 bit), 60Hertz
1024x768, True Color (32 bit), 60Hertz

11 Additional Valid Modes for use only with 17" & 18" LCD Monitor
1280x1024, 256 colors, 60Hertz
1280x1024, High Color (16 bit), 60Hertz
1280x1024, True Color (32 bit), 60Hertz

http://www.google.com/#hl=en&source=hp&q=power+adapter+for+the+CTX+Monitor+S500&btnG=Google+Search&aq=f&aqi=&aql=&oq=&gs_rfai=&fp=ff274912d96214e6

Hi,

please try doing a factory reset of the monitor.
please press the menu button on the monitor itself. you can easily locate the buttons below or on the right hand side of the screen on the monitor panel.
select the factory reset /recall options with the help of the arrow/+ - buttons.
this would reset your monitor color settings to default.

CTX 15"1024x768 TFT LCD-Black Monitor · i have a ctx moniter says ... Answer. i have a ctx moniter and wen i plugnitin to pc tower itsays undeceted mode watdoes this mean. Close Close. ASUS Eee PC 1000H

that probably the highest ur screen can go unless u update ur video card u can purchase some really good video cards at Best Buy or Wal mart Looking to help u Shaun

Searched the CTX site found the device in discontinued products but no link.

This one actually has 761 in the name -- you did not list what you have found so I hope this is new.

http://members.driverguide.com/driver/detail.php?driverid=517451

look for cold solder joints on the crt neck (color circuit) board!

did you try the mode reset switch on the monitor after going back to 800x600? also try 640x480/16 colors since that is one of the default modes for all vga monitors.