Change color should work. I assume you only want the blue lettering to change.
Use the eyedropper to select your lettering color.
Set a keyframe for Hue Transform at frame zero.
Set a new value for Hue Transform at the 30 second mark.
Can you post a screen grab that includes the effect control window and the timeline?
Apply a Tint effect and animate one of the colors.
1. Use the eye dropper to select the blue color of your logo. Right now it's orange?
2. Check the invert color correction box.
3. Set keyframes for hue, lightness, and saturation.
4 at the 30 second mark, set saturation to 100, lightness to -50 and you should see the white turn to a color. Play with the three controls until you get the color you are looking for.
You have to carefully read the labels in the Effects Control Panel:
As Donald pointed out you did not select the color to change, it looks like you chose a new color. I don't think this is the best effect to use to do what you want to do. When you have problems with an effect type the name of the effect in the Search Help field at the top right corner of AE and check out the community resources. That's the fastest way to learn.
I have a couple of questions. First, did you change your background color of the comp to white? Does that PNG have transparency?
If there is no transparency then you can easily create transparency in the background of the PNG in Photoshop then add a layer below the PNG file to make the background any color you want. If you used a shape layer you could animate the fill color or even animate the fill color of a gradient fill.
If you don't want to go to the trouble of creating a transparency in the PNG and the image quality of the PNG is good then you might want to try putting a shape layer below the image and then adding the Extract effect from the Keying Menu. Play with Blue or Luminance and you can get something like this:
If you are really new I wold start here: Basic AE and maybe consider looking at Adobe TV to get a handle on the UI and the basic tools. AE is a professional app every bit as complex as an F-18.
You wouldn't expect to get off the ground without at a little homework.
AE is a professional app every bit as complex as an F-18.
I would much rather crash After Effects.