Sprite changes colour when imported into Unity

Question

I create some simple geometrical shapes in Inkscape, then export it to PNG and import into Unity.

Positive example: I make a rectangle of colour hsva(0, 0, 32, 255), export it as a 32x32 PNG image and import to Unity. Then I put it into the scene. When I check its rendered colour with a probe tool it's perfectly correct: hsva(0, 0, 32, 255).

Negative (problematic) example: I create a right triangle of colour hsva(0, 0, 32, 255), export it as a 32x32 PNG image. Effect: half of the image is transparent and the triangle edge is "anti-aliased", but the main triangle's area in the PNG file still conserves its original colour.

Then I import it into Unity and I put it into the same scene and check its rendered colour with a probe tool. It's actually hsva(299, 8, 33, 255) - very dark purple, but still distinguishable from the (0, 0, 32, 255).

What am I doing wrong? Why is the rendered colour of the sprite different? How can I solve this problem?

Thanks in advance for your help :)

PD

Adding my import settings, as requested in on of the comments (now I'm experimenting with larger images 512x512, but the effect is the same):

Answer 1

Thanks @DMGregory and @Draco18s for help with this one!

The problem turned out to be the compression algorithm which Unity automatically applied for the imported image. The DXT5 compression reduced colour precision, provoking the subtle change in the rendered colour of the sprite.

The solution to the problem was changing Compression Quality from "Normal Quality" to "High Quality" in the default import settings for the image.

This could be also solved by explicitly overriding the compresison algorithm in the build-specific settings of the image, selecting BC7 compression algorithm for instance.