One of the TV's I use with my Roku is a 1995 CRT RCA. I use the RCA cables (Yellow, red, white) for the connection. This TV is set up so it has a special channel 00 That shows whatever is connected to the RCA input jacks. I use my TV remote only to go to the Video Channel 00 and then I use my Roku remote to actually control the Roku itself.
My other TV is a HDTV with RCA input jacks. It's input selection lists all jacks, such as HDMI, RCA, etc., I use the TV remote to chose the input to watch (being the RCA Video (yellow) and audio (red and white).
I don't understand why you lose the color except it might have something to do with using your TV remote to control the Roku. Do you have the Roku remote that came with the box? Have you put your TV on the channel that can input from your RCA input jacks? Then once the TV is showing Roku, use the Roku remote?
The only other remote I know of that handles Roku okay is a Harmony Remote, which I do have one. However, I use the TV remote for the TV itself and when I want to watch my DVD player or the Roku, I use the TV remote to go to the area where they will be input from and use the player or Roku remote to watch whichever of these inputs I have selected. I do have an A/V switch so I can send any of the accessories to my TV A/V input jacks.
Maybe the above will give you some more clues to try. I think there is a way to solve this but it is hard to give advice not knowing your actual setup of connections and the brand names of what you are trying to interconnect.
Anyway, hope this helps.
Original Roku Model N1000,bought 2008 (2014 still works perfectly)
2014 new owner of Roku 3500 (HDMI) streaming stick