1. Create a stained glass panel for a special window.
2. Play around with neon light strips to create surreal effects.
You can find neon light strips here that change color via remote control. You can install these along the trim, under your bed, or in a specific room like your bathroom. As for signs, you can check out this site here for custom made neon signs or try doing it yourself here.
4. Splash some color onto your pillow covers.
You'll need denim or canvas fabric and some fabric paint (or acrylic will work too). More details here.
5. Frame your pictures with colored tape.
6. Dye some tassels in Kool-Aid.
Major plus: it'll smell deliciously sweet too. Learn how to do this here.
7. Scatter some geometric decals in no particular arrangement.
8. Accent your mirror with neon hues.
9. Spruce up the legs of your tables.
You can dip-dye or spray the legs of your table. See more instructions here.
10. Bedeck your stairs with multi-colored and mismatching tape.
11. Consider making your room two-toned or three-toned.
12. Inversion works great too.
Whoever says grey isn't a ~color~ doesn't understand the subjectivity of color.
13. Add paint to highlight doors and other furniture pieces.
14. Color block with subtle geometry.
You'll need some paint tape and a willingness to pull out some middle school math. Just think of it as paint-by-number for adults. See some more detailed instruction here.