I went round a similar path a few years ago with the later HD350 (RS10). The cheapest fix is just to turn the colour and tint controls down a bit...however that in no way fixes the problem in terms of accuracy but for some that is enough. Next up is a used Lumagen HDP or HDQ that has a limited control over the primaries and again while it won't measure accurately, subjectively it is a step up from the above option.
Beyond that you get into external CMS options such as the Video EQ I tried for a while: It pretty much nailed the colours spot on, but the back up was very poor and I sold mine on and replaced it with a Lumagen Mini3D which now has the later 125 point automatic calibration. The colours, greyscale and gamma are absolutely spot on (using an i1D3 Pro sensor) though I now have the later X35 (RS46) which has more accurate colours to start with. However the Mini3D costs more than used RS40 let alone a used RS1/HD1, so it's a disproportionate fix for an older projector I suppose.
There is also the DVDO Duo which has a CMS, but I'm not familiar with this model (I did own the more basic DVDO Edge that was used along with the Video EQ). Not sure at all about used prices for the Duo.
At least that should give you some real world experience even if the 'best' fix isn't financially viable.
What might be worth looking out for is a used RS20/HD750 as it has a built in CMS (you'd still need some way to calibrate it though as you would for most of the above options to get the most out of them). The RS20 has 50,000:1 contrast compared to 15,000:1 of the RS1 so the blacks are also much deeper for the same brightness level. It may work out cheaper than an RS1 plus an external CMS though.
"Don't believe everything you read on the internet". William Shakespeare 1615