In general I agree and have found it really hard to find tools which work well for different degrees of impaired colour vision. I've tried a few apps which are

In general I agree and have found it really hard to find tools which work well for different degrees of impaired colour vision. I've tried a few apps which are supposed to show how things look for me and the results are almost always not quite right. I will say that I can barely tell the difference between the original example image on this page and the deuteranopia one. According to tests I have a moderate deuteranomaly.