This is a section of the tutorial Making an Accessory.
To customize the look of your accessories, you need to edit the textures in your preferred image editing software. In this tutorial, you will see how to use basic GIMP features to make quick changes in the product’s textures. To get the image files that you will need for editing, see the Making an Accessory tutorial.
Editing the Frame and Lenses
STEP 1. Open the texture in GIMP by clicking Open and navigating to where your frame texture is saved, or by dragging and dropping the image into GIMP.
STEP 2. Create a new layer on top of the original image.
To make sure the colors display properly, go to Image ➞ Mode and choose RGB.
STEP 3. Click on the Rectangle Select Tool and highlight the area of the glasses’ bridge (the gray area of the texture).
Then, go to Select ➞ Invert to select everything else except the bridge.
STEP 4. Change the Background Color to a different color of your liking. You can choose the color from the palette that pops up when the background color is clicked.
For this tutorial we are using the HTML Notation field the value of 32bbb3
You can also set the Foreground Color with the Bucket Fill Tool, but you will need to make sure the tool is set to Fill Type ‘FG color fill’
STEP 5. Click on the Bucket Fill Tool 
on the left toolbar, then click on the selected part of the image. This will apply the selected color.
STEP 6. Change the Layer Mode from Normal to Darken Only to see the changes on your texture.
STEP 7. Save the image by going to File > Export As. Select the folder where yo want to save the texture, and save it as a .jpg file.
STEP 8. Follow the same instructions to load and change the color of the lenses texture (the white image you downloaded). Make sure to save it as a separate .jpg file!
Editing the Opacity Map
STEP 1. Load the grayscale opacity map that you downloaded into GIMP.
STEP 2. Add a new layer above the map.
STEP 3. Change the Background Color back to white (HTML notation: ffffff), and make sure the Foreground Color remains black.
STEP 4. Click on the Gradient Tool button. Click on Tool Options, then the Gradient button. Select FG to BG (RGB).
STEP 5. Drag the cursor across the image to create a gradient. You can drag across any direction you wish, but note that the black (the opaque part of the texture) will be concentrated on the point where you start the gradient from.
STEP 6. Save the image by going to File > Export As. Select the folder where you want to save the texture, and save it as a .jpg file.
Now that you have made your textures you can return to the Making an accessory tutorial and continue Creating Your Product.