I think choosing a different plant species light be the best option, there are plenty of nice colorful plants to chose from. L panatnal, L granulosus/perunesis, Myrio "red matogrossense" etc. These do not change color too much.
This is my tank with the plants using EI:
The pic below, I could play with photoshop and enhance the red coloration a good deal and still retain the greens, but there's a certain unnatural color to it and I know what photo software does as well as flash and lighting for photography. Many alter their color, particularly for contest.
My color on the Wallichii is much better than the photo suggest. It is a really pretty plant.
At the surface, the plant develops a nice color, less so 1/2 way up in the water column.
So let the plants grow, then hit the surface for awhile.
Trim R wallichii by uprooting and replanting the tops only. It does poorly if you top it and wait for new shoots to regrow.
Polygonum, Alternathera etc are nice colorful plants as well or Ammannia, but it's too big for your tank.
The hardscape is well done, belem hairgrass is an excellent choice.
What about mossy wood, say Fissidens to add contrast from the hairgrass, instead of bright green weedy Bylxa? Behind this dark moss, then a wider leaf bright green plant (Starougyne, Downoi, a Crypt, Hygro kompact, red plant of choice etc), then in the rear, the light fine leave wallichii?
Most of the plants I list sell well also, look nice, are slower growing and easy to care for.
All good attributes.
Regards,
Tom Barr